Recommend Pathfinder's Funnest Book?

[Palanan]

So, the holiday gift card happened. It was generous. And once again, I am tempted by Pathfinder.

But despite the generosity, I don't want to go all-out for the APG, CRB, ACG, or any of the other big-ticket items. I'm interested in something a little less pricey, that's interesting, useful and fun.

Possibly even quirky. Any suggestions?

[Pokonic]

City of Strangers is kind of neat, in my opinion. Naga lords, troll seers, blood mages, there's some good material in there to use, because there's enough stuff in the book to spread out over a entire game.

[BWR]

"Distant worlds (http://paizo.com/products/btpy8qib?Pathfinder-Campaign-Setting-Distant-Worlds)", detailing Golarion's solar system.
It's brilliant, with Barsoom all but stolen whole-cloth, planets full of undead, giant sentient jellyfish and gas giant societies, and plenty of adventure hooks.

[N. Jolly]

For a paperback, I'm a fan of Undead Revisited, I have the PDF and I quite enjoy the description and stories behind the undead.

[Palanan]

I appreciate the suggestions so far. Still open to others.

What do people think of Champions of Purity? It looks like sort of a mini-BoED for Pathfinder, but at 32 pages I'm not sure if it would really be worth it. Anything decent in there?

.

[NamelessNPC]

I think the aasimar alternate racial traits are there. They become the most versatile race with those

[Ssalarn]

Champions of Corruption, while evil-themed, has a lot of fun stuff in it. The Betrayal feats are entertaining (though we immediately houseruled away the silliness about people they're shared with not being valid abettors), and it's got the "Kool-Aid Man" feats that let you bust through walls in spectacular fashion.

Blood of the Moon isn't everyone's favorite, but it is one of mine. It's got skinwalkers, Paizo's answer to the 3.5 shifters, and they're well executed, flavorful, and fun.

Inner Sea Combat is a really good one; it's thicker than a Player Companion splatbook but still softbound and affordable, and it has a ton of cool feats and great archetypes in it. There's a paladin/monk MCA that's a personal favorite, feats to allow you to gain a hippogriff, worg, or other magical beast as an animal companion, and some fairly decent fluff for Golarion as well.