For anyone at least somewhat familiar with Dungeons and Dragons 3rd edition and Dungeons and Dragons 4th edition, this book is clearly an attempt to take some of the ideas the author liked from fourth edition and fit them into third edition. And as far as attempts go, it's superb. The art is also great, and the setting is a nice mix of steampunk plus steampunk-biotech plus traditional Dungeons and Dragons -style fantasy.
Characters have the six Dungeons and Dragons stats with normal bonuses (typically -4 for awful ratings up to 5 for awesome ones). Characters have a race, one of human, elf, dwarf, gnome, lizard-man, goblin, goliath, and about a dozen others. Characters have one or at most two classes, i.e. professions, out of Bard, Barbarian, Elementalist, Fighter, Monk, Necromancer, Invoker, Warlock, Sage, Thief, Sorceror, and about a dozen others. The character experience is rated in levels, from 1 for beginners to 20 for the best. Each class has a huge selection of special abilities the character picks from as they gain in levels, covering things from a bonus to stealth to extra damage with a favorite weapon to summoning earth elementals, based upon the class.
Feats are gone. Skill points are gone. Spell lists are gone. Everything is governed by the special abilities given to each class. The game has many options, great artwork, and great flavor, but a lot less of the complexity that plagues Dungeons and Dragons 3 or 4, or a lot of related Open Gaming License (OGL) derivatives of Dn