Summary of the Main Mechanical Points So Far
Keeping in mind that we're in an overview section and the actual coverage comes later, the main differences from standard D&D are that you roll 2d12 instead of 1d20; each d12 is associated with a currency; one for helping you and one for hurting you; there are limits to how much of that currency you can accumulate.
Those currencies are Hope and Fear, and they allow you to activate abilities.
There are two 'condition' tracks, hit points and stress. Using abilities can accumulate stress while taking hits can cause hit point damage. This sounds like Lancer has been described to me.
Relative to D&D, the number of hit points is very small. But you're not directly applying rolled hit point damage. Instead there are thresholds for damage; every hit does at least one damage but if you exceed a threshold you do 2 damage, and if you exceed double that threshold you deal 3 damage. Armor appears to have a very big impact on damage thresholds and level seems to have a minor impact.
Step 6: create your background
In addition to choosing weapons and armor in the last step, you also get a bunch of minor equipment and pretty much any minor items that you want if they don't provide a mechanical benefit.
For background, they have several questions they ask - they're just suggestions and you can make any background you like, really. Since play starts at Level 1 (at least, it assumes that and suggests that for new players) I'm surprised there isn't anything about avoiding an epic background that exceeds a character's competence. They haven't done anything to establish what a 1st level character OUGHT to be able to do, or talked about their abilities, so this remains very abstract.
Step 7: Experiences
These are kinda background traits, but they actually matter in play. You get two to start and whenever it applies to something you want to do, you can use a Hope point to pick up a +2 on your roll. If both of your experiences apply, you can spend 2 Hope and get a +4 on your roll. Keep in mind that you're 50% likely to pick up a new Hope on this roll, so there probably isn't too much reason not to use them generally. There's some explanation of what a good Experience is - not too broad so it applies all the time (Focused) or too limited mechanically (One-Hit Kill). An example of a 'good' Experience is 'Assassin of the Sapphire Syndicate'. Assassin would be okay, but it doesn't clearly offer out-of-combat options. The social aspects of being connected to a syndicate make it better.
They have 5 categories of sample experiences including backgrounds (Circus Performer), characteristics (Friend to All), specialties (Swashbuckler), skills (Quick Hands), and phrases (No One Left Behind). There are about a dozen in each category.
Step 8: Domain Cards
So every class is associated with 2 domains (see the chart above). At 1st level you an pick two 1st level Domain cards. These are abilities (maybe spells, maybe not) that you can choose to activate. You can choose one from each of your domains, or two from the same domain. They strongly suggest that different players avoid taking the same domain powers - since each 'neighboring class' on the chart shares a domain with a class, it's definitely possible to have characters with access to the same domain.
It's not talked about here, but you're limited to how many cards you can have 'in hand'. As you gain levels you gain more cards and if you want to activate a card that's not in your hand you'll pay a cost (probably stress). Skipping 300 pages to look a Domain Cards, the Arcana Domain (Sorcerer/Druid) has Rune Ward, Unleash Chaos, and Wall Walk as 1st level options. Rune Ward allows you to spend 1 hope and reduce damage by 1d8. To Unleash Chaos you make a Spellcast roll against a target. You can deal 1d10 per Spellcast trait. Recharging it costs 1 Stress. I don't know what your Spellacasting Trait is yet (I don't think that's one of the six traits we've already talked about). Wall Walk lets you spend 1 Hope to let a creature walk on walls until the scene ends.
Bone (Warrior/Ranger) offers Deft Maneuvers (take a stress to get to anywhere on the battlefield without having to make a roll); I See it Coming (spend 1 stress to get +1d4 to your Evasion); or Untouchable (gain a bonus to your Evasion equal to half your Agility.
At this point it appears that your Traits range from -1 to +2, and 5/6 of them are +1 or less. Untouchable seems like a really useless power at 1st level where the maximum bonus you can get is +1 assuming you put a 2 in Agility. Getting +1d4 is much better. Maybe you can raise your Traits quite a bit somewhere, but since Domain Powers are supposed to be pretty important I'm already concerned that there are some bad choices.

You've chosen Untouchable???
Step 9: Create Connections
This is how you know the other characters.
The next couple of pages show a sample character sheet filled in for a Sorcerer. I found a similar one on Twitter, so check it out:
The picture above lists a minor damage threshold of 3 (major 8 and severe 13). That appears to be something that changed in the playtest. What I see is anything less than 7 is minor damage. It appears that at one point you had a minor damage threshold and anything below that dealt one Stress. Since Stress is limited, taking stress might be worse than taking damage, I'd expect, depending on the situation. There's a second page for the sample but it mostly has suggestions and you circle the ones you like. For example, you can have Skin the color of: ashes, clover, falling snow, fine sand, obsidian, rose, sapphire, wisteria.
The bottom 3rd of the second page has level-up instructions. The game has four tiers; tier 1 (1st level only), tier 2 (2-4), tier 3 (5-7) and tier 4 (8-10). Each time you level you get to choose two options from a list. Some options can only be chosen once, some 2x and some 3x. Each has a box that you check when it is done. Some instruct you to 'check' something else. For example, at level 2 you can choose a +1 bonus to two traits. Then at level 3 you can choose a +1 bonus to two traits, but they can't be the same ones you did the last time. At 5th level you can 'erase' those marks', so you can do it again.
Domains
There's another section giving pictures of the Magic:the Gathering like symbols for each of the nine Domains, and a color. Each has a paragraph description. To me it feels a little like the D&D 3.x explanation of why Mialee is chaotic because she sees her magic that requires intensive study as an art and Ember is lawful because she sees her art art that requires intensive study as a science - or something similarly contradictory and vague.
Arcana is the domain of innate and instinctual magic. Sage is the domain of the natural world and the power of the earth to unleash raw magic. Codex is the domain of intensive magical study. Splendor is the magic to both give and end life.
This is followed by a 'reading domain cards' infographic. Every card has a level and a symbol/color denoting the domain. The recall cost (paid in Stress) can bring a card to your hand if you hadn't 'prepared it' and have a full hand. It also lists a type (ability/spell/grimoire) and then rules text that explains what it does.
We're now on page 28 and we're heading into the full class descriptions - 24 pages of class descriptions (9) and sub-classes (2 per).
Each class determines what domains you have access to, starting evasion (AC), starting hit points, items you get to start with, a unique class feature (or more than one, maybe, sometimes), and a special move you can make by spending 3 hope.
Each subclass determines your Spellcast Trait (if you cast spells). So yeah, apparently the reason I don't know what your Spellcast Trait is is because it depends on your class; presumably Intelligence for Wizards and Charisma for Grace casters.
Subclasses also determine a Foundation feature, Specialization features (something you gain when you level up), and a Mastery Feature (also granted at higher levels). It warns you that the class descriptions have a ton of information related to the rules that you haven't learned yet and will be covered in the next chapter. Which is probably true, but I've looked ahead and I am afraid...very afraid.
Covering every class and sub class seems like it would take quite a long time, so I'm going to look at just a couple to provide a sense of what we're talking about.
Seraph
Remember the cover picture? Remember the winged warrior flying around? Apparently that's a class. Seraphs are divine fighters and healers imbued with sacred purpose. Basically paladins.
They have access to the Splendor and Valor domains, get an Evasion of 9 and 7 Hit Points. They can spend 3 hope to remove a hit point of damage from an ally (remember that mostly means +1 hit at 1st level). Both subclasses use Strength as their Spellcasting Trait. At the beginning of each session, roll 1d4 for each point of Strength you have. These are called 'prayer dice'. You can use a die to reduce incoming damage, add to a roll's result after it has already been rolled, or gain Hope equal to the result - for yourself or an ally.
The subclasses include Divine Wielder (you get a legendary weapon) but I'm going with Winged Sentinel - you fly. While flying you can take 1 stress to pick up a willing creature and carry them, or spend 1 hope and deal +1d8 damage on an attack. When you're flying you gain advantage on Presence Rolls. When you succeed with Hope on a Presence Roll you can either gain +1 Hope (normal) or take away 1 fear from the GM. I don't know what rolling with advantage means here - it hasn't come up before. It says Specialization happens at 'higher levels' but nothing here says when or how.
Eventually you get the Mastery Features of Ascendent (+4 to your Severe Damage threshold) and Power of the Gods (deal 1d12 instead of 1d8 while flying). Not gonna lie, an extra 2 damage as a high level ability only usable while flying seems pretty lame.
So I'm looking at domain cards. Remember how we have a class ability to spend 3 hope to clear 1 hit point? I could take a spell that lets me heal 1 hit point for 2 hope instead, but it also takes longer. Probably better to take
Beacon. Make a spellcast roll and if you succeed a target within far range takes (d8xProficiency)+2 damage and becomes
vulnerable until the condition is cleared.
So what is proficiency? It's 1 at level 1, but as you gain levels you can raise your proficiency. All regular weapons deal the base weapon damage x proficiency, so it's a scaling damage mechanic.
One of the Valor abilities is
Bare Bones. When you're not wearing armor, you count as if you are, and the base damage is 10/20 at 1st level. That seems pretty solid. Combine it with 'I am Your Shield' and you can take your allies damage and apply your armor multiple times (taking stress for each time).
Wizard
Domains: Codex and Splendor
Evasion: 11
Hit Points: 5
Class item: book or harmless pet
Hope Feature: Spend 3 hope to force an enemy to reroll an attack or damage roll
Class Features: Prestidigitation - at will minor magic. Strange Patterns - pick a number between 1-12; whenever you roll that number on a duality die gain a Hope or clear a Stress.
We could choose School of Knowledge, but we're going with School of War.

School of Rock wasn't an option
We use Knowledge as our Spellcast Trait (as does a Knowledge caster, so maybe our CLASS is really what determines it, but maybe when they release more subclasses that'll change???). The Foundation Features are that a I get +1 Hit Point and when I succeed with Fear on an attack roll, I deal +1d10 magic damage.
When I get specialization, I can conjure a shield which lets me spend 2 hope to add my proficiency to Evasion. I also get Fueled by Fear where my extra magic damage increases to +2d10.
When I get Mastery I can take Stress to deal +1 Hit Point (not damage, an actual hit point); I also get Have no Fear and the damage from before increases to +3d10.
Codex Domains give you 3 unrelated spells (that codex is unique). My Battlemage can take Book of Ava or Book of Illiat, or Book of Tyfar. Of course those names don't mean anything to you or to me, but they determine which 'spells' I can cast. Ava gives me 'push someone to far range and take 1d10 damage', spend a hope to give someone +1 Armor Score, get an ice spike to deal Proficiency x d6 damage to someone. If I chose Illiat instead I would put someone to sleep, or fire magic missiles, or spend hope to telepathically communicate.

I know they said I could flavor my magic, but apparently Wizard Elsa is not the right way to go
For reference the following is a list of Class(Subclass 1/Subclass 2)
Bard (Troubadour/Wordsmith)
Druid (Warden of Elements/Warden of Renewal)
Guardian (Stalwart/Vengeance)
Ranger (Beastbound/Wayfinder)
Rogue (Nightwalker/Syndicate)
Seraph (Winged Sentinel/Divine Wielder)
Sorcerer (Elemental Origin/Primal Origin)
Warrior (Call of the Brave/Call of the Slayer)
Wizard (Knowledge/War)
Just looking at class abilities, I feel the way I do about 5th edition. They just don't seem that interesting and your class does the same thing at all levels of play. Domains may really impact that as I haven't looked at many of the Domain Powers. I will say that I'm quite disappointed with the Wizard. I would at least prefer that the spells on each card share some kind of theme. Particularly for a new RPG, I would hope they'd spend some effort on a metaphysics of magic to explain what magic can and can't do
and why. For any RPG, I highly recommend
incorporating Sanderson's Laws of Magic.
I'm taking a break, but if anyone wants to know more about any of the classes/subclasses, let me know. Otherwise we'll hit Ancestry next.