I bought this book for rules materiel to import into my own projects, rather than as a system to use in its entirety. This colors my perceptions of the product, but I definately do like what I see.
It starts out with character creation, which replaces the standard Pathfinder race system with an origin system, which gives you ability score adjustments and features based on your upbringing and social position. This is a clever idea, even for settings that do include playable races other than human. I'll probably end up using this in a modified form.
Next is some classes for early 20th century games. Each class gets an armor class bonus to compensate for low availability of armor. We get the Soldier, which is basically a Fighter with Gunslinger deeds. This pretty basic (not that the Fighter isn't), but mechanically solid. Next is the Aristocrat, which seems to be a social focused Rogue. It gets a bonus feat every other level, which has a reasonable selection of combat feats, and aristocrat talents every level it doesn't get a feat (the talents focus on social bonuses). This one I think needs additional combat power, as it doesn't seem to get a lot of combat abilities and only has medium BAB. The Explorer is pretty much a Ranger with favored terrain from first level, no favored enemy, and no spells. It likewise doesn't have quite enough combat power in my eyes. The Scoundrel is a more stealth focused Rogue, with no sneak attack except a talent that adds critical damage, some bonus feats, and a scaling stealth ability. The talents provide good stealth and movement, but not quite enough combat utility. The Priest has channel energy for 1d6 healing/damage per 2 levels, domains, and 0-9 level spellcasting. So, basically a Cleric. The Mystic is basically a Wizard, with Arcane Bond, Arcane School, a handful of bonus feats, and 0-9th level spellcasting. The classes are a weak point of the book, as the Explorer, Aristocrat, and Scoundrel seem to have traded combat power for non-combat utility when compared to the Pathfinder classes, which makes them less useful in a fight. With the Soldier being about on par with a Fighter and the Spellcasters barely changed, the fact that three classes are weaker than Pathfinder and three the same presents a problem. It isn't too hard a problem to fix, just a matter of allowing Aristocrat and Scoundrel players to access the Rogue and Ninja talents and increasing the number of uses for per day talents (which should be done in any Pathfinder game, really), and tacking the Skirmisher Ranger archetype onto the Explorer, so I'll only take away half a star for that, but I can't recommend using the classes as-is.
The Feats and Skills chapter only has one feat, Mad Scientist, but it is a good feat. It basically allows non-spellcasters to craft items as if they were spellcasters. The three skills are the Craft, Drive, and Pilot skills needed for vehicles.
The Firearms rules are solid enough, being better than D20 Modern and not relying on Reflex saves, and the generic firearm stats are solid enough. The chapter with gun rules and stats also has basic adventuring equipment and cost of living figures for different lifestyles, and gives a few mad science alternatives to spells like raise dead and restoration.
The next chapter is vehicle rules. They look solid enough, but I've never used vehicle rules before, so I lack a basic for comparison.
Spells adds some new spells that deal with modern technology, and explains how some old spells work with new technology.
Prestige classes include the Mad Scientist, which gets an item creation feat every other level and greatly increased ability to mimick spell lists when creating items. The Private detective gets perception and luck bonuses and a couple of bonus feats.
The next chapter is an example setting, which is a pretty basic Roaring 20s city. Given that this is supposed to be an example, I can understand why it is so basic.
The final chapter is tips for GMing, which explain the basics of the pulp genre in good detail for a basic overview and provides some slang and links to further research.
This document has its fair share of ideas and rules I can borrow, which is what I bought it for, so I'm pretty satisfied. Aside from taking off half a star for the classes, I don't have any complaints, which leaves me at 4 1/2 stars, which rounds out to five.
[5 of 5 Stars!]