...or horrible robots with chainsaws, which is a decent proxy for science.
So, this is a GM-focused book, but with a bit of PC material. The first three chapters are fairly quick, covering general construct construction, archetypes, and magic items. By and large, this section is decent but not exceptional. A few good archetypes (I particularly like the Construct Caller Summoner and the Voice of Brigh Bard), some interesting items (an Automaton Core is a minor artifact with actual methods for PCs or NPCs to get, if they're not very nice), and a bunch of golem manuals.
The meat of the book is the fourth and final chapter, which occupies 2/3rds of the page count. And this has some beauties.
First up are the Automatons, which are my new favorite thing in Pathfinder. Short version, in ancient days the Jistka Imperium was waning, and so as a way to preserve it some of the elders of the Imperium started uploading their citizens minds into thaumaturgical robots. Thus you have the living constructs known as Automatons, ranging from the adorable and familiar-grabbable Familiar Automaton to the mountain-shredding CR 20 Master Automaton. These guys have everything. Imposing stat-lines, gorgeous art, fascinating backstories, oodles of plot-hooks... you want it, you got it.
There are a bunch of new robots, golems, and clockworks. The stand-out here is the CR 17 Gladiator Robot, which is what happens when you give a hyper-effective killing machine a chainsaw and a directive to please the crowd. This thing is basically a slasher movie villain, and thus awesome. At the other side of the spectrum is the Clockwork Goblin, which is small and silly and kind of adorable.
Finally, there are templates, a half-dozen of them. Golems wreathed in caustic mist, constructs haunted by ghosts, constructs with artificial psychic minds, constructs with someone else's brain stuffed into them, commando constructs (as scary as they sound), hilarious malfunctioning recycled constructs, and the most awesome, steam-powered mechanical dragons.
Allow me to repeat: steam-powered mechanical dragons.
Conclusion: This is a GM book primarily, though a few of the archetypes are nice for a PC. It is a very good GM book, useful if you want any kind of constructs in your game.