So I made some quick cheat-sheets for classes and chapters, since the information is scattered around and sometimes hard to find. These books could have been a lot more organized...
These are the Specialization/Classes you can choose, what buffs they get, and their general skill progression:
ALL:
Power Armor
Bolt Pistol
3 Frag Grenades
3 Krak Grenades
Combat Knife
Repair Cement
Apothecary:
Reduce corruption OR Create toxins OR Enhanced healing
Cheaper Int, Per
Chem-Use/Medicae/Etc
+bolter
+reductor (gene-seed-harvester)
+narthesium (medical)
Assault:
+Swift Attack
Jump Pack specialization OR +Horde Damage
Cheaper Agi, Str
Dual-Wield/Agility/Disarm
+Chainsword
+Jump-pack
Devestator:
Entrenched heavy weapon OR +Horde Damage
Cheaper Ranged, Str
Ranged Superiority
+Heavy Bolter w/ backpack
Librarian:
It's a Wizard, they're complicated...
+Bolter
+Force weapon
Tactical:
+Command
Bolter mastery OR *Share squad abilities cross-chapter*
Balanced
"Field General" skills
+Bolter
+<25 req special ammo (1 clip)
Techmarine:
Reinforces cover AND Servo-Arm
Cheaper Str, Int
Tech-Use/Bionic Fuckery/Crafting
+Bolter
+Servo-Arm (built into armor)
+1 Cybernetic
These are the different Chapters you can choose from, their buffs and their unique abilities:
Black Templar:
+5 Melee
+5 Willpower
-Devestator
-Librarian
SOLO - Righteous Zeal: Ignore enemy toughness, +toughness, vs daemons/psychics. ~+to-hit, +damage, ignore warp weapons
SQUAD - Holy Vengeance: Continue melee until you miss.
SQUAD - Armour of Faith: +Psychic Resist
Chapter Skills: Interrogation, Witch Hunting
Blood Angels:
+5 Melee
+5 Agility
SOLO - Blood Frenzy: Once, reroll melee damage. ~+Penetration, +Righteous Fury
SQUAD - Fury of Snaguinius: +Melee, +Strength, +Toughness
SQUAD - Feel no Pain: 1/2 damage received
Chapter Skills: Acrobatics, Berzerk
Dark Angels:
+5 Ranged
+5 Intelligence
SOLO - Stoic Defense: +Temporary Toughness.
SQUAD - Sustained Supression: Overwatch + Normal.
SQUAD - Immovable Defense: +Ranged, +Dodge, +Armor
Chapter Skills: Lore
Space Wolves:
+5 Perception
+5 Fellowship
-Apothecary
SOLO - Wolf Sense: +Perception
SQUAD - Tooth and Nail: +Outnumber, +Melee
SQUAD - Pack Tactics: Enemy cannot dodge/parry melee
Chapter Skills: Alcohol, Performance, Tracking, Wrangling
Storm Wardens:
+5 Strength
+2 Wounds
+Sacris Claymore
SOLO - Thunder's Call: Pull agro vs one enemy.
SQUAD - Lightning Strike: Immediate surprise round.
SQUAD - Shield and Sword: Fellows can parry for others.
Chapter Skills: Tracking, Gambling, Knightly combat
Ultramarines:
+5 Any
+5 Any
SOLO - Favored Son: +Cohesion
SQUAD - Lead by Example: +Fellowship to tests
SQUAD - Rally Cry: Restore Cohesion
Chapter Skills: Command, Tactics
SOLO abilities can be activated at any time. SQUAD abilities can only be done when nearby at least one other marine, and CANNOT be active at the same time as your SOLO. Most SQUAD abilities either give a benefit to the entire group, or benefit one individual more when there's more people involved. AND, chapter specific SQUAD abilities only affect others who are in the same chapter as you, except for Tactical marines can share their chapter abilities with the entire squad.
This list does NOT include default buffs, skills, and abilities, which are available to all marines. Instead these are just the specific class/chapter qualities.
For my game, I'm considering just forbidding Librarians, as they're complicated and just prone to being frustrating for everyone...