Name an Awesome Book

[Fizzlemeyer]

Several things leap to mind here;

The first being the Mortal Engines Series by Phillip Reeve.  http://en.wikipedia.org/wiki/Mortal_Engines_Quartet The series involves enormous cities roving about the blasted wasteland of Europe physically consuming other cities.
Also two words:  Municipal Darwinism. http://en.wikipedia.org/wiki/Municipal_Darwinism

Anima Beyond Fantasy, which I own and believe to be a beautifully illustrated book, filled with interesting races, cultures, character classes, and a fascinating twist on the idea of an ongoing war between good, evil, light, and shadow.  Also one of the most interesting things from the book was that you could individually level different skills, with your character class determining what percentage of your experience points your could spend on certain aspects of your character.  EG: a mage could only spend about 30% of her experience points on melee skills, while a warrior could spend up to 70%.
http://en.wikipedia.org/wiki/Anima_Beyond_Fantasy

And naturally Scion and Exalted, Truly bad ass settings both, and in quite desperate need of streamlining / revamping if not necessarily a full overhaul or system reboot.

[Hida Reju]

Old Pre D&D Wizards of the Coast book series called the Primal Order. Basicly how to make gods witht he capital G again. It gave a system that adapted itself to almost any other game that allowed you to put gods in their own power bracket and be untouchable by normal mortals.

Also gave info on building religons handling clerics and paladins. Basicly to me it was GOD: the RPG.

[Necrosnoop110]

My old AD&D Dungeon Masters Guide (1E) because of all the charts, tables, appendices, and wordings.

Another vote for D&D Heroes of Horror (3.5E) it contains wonderful plot hooks, story seeds, setting and adventure ideas; in fact the whole book is crammed with them.

D&D Lords of Madness (3.5E) offers rich flavor and tons of background information on one of the toughest races to roleplay well, aberrations.  



  

[Amechra]

I second the good old AD&D Core books, just because you can oftentimes just feel Gary Gygax's excitement, back at the forerunner of the system...

Plus, just reading through the oftentimes cruel magic items is a treat in and of itself.

As for flavor, Dwarf Fortress is nice, though that is a computer game.

However, for shear world building, and something to take notes from, may I recommend the Malazan Book of the Fallen? Looooong series of doorstoppers, where the line between mortals and gods is just plain frayed. I mean, when there is a character whose nickname is The Emperor of a Thousand Deaths, and one character comments that they're exaggerating, it's only been a hundred or so...

Also, it's just plain great to grab ideas for religion from.

Also, Redwall, for the nostalgia and fun it brings me. I've always thought it should be adapted into an RPG; the closest thing flavorwise would have to be Mouseguard, though.

Also, I like looking at Risus, just for the clarifying simplicity and the reminder that rules aren't important next to having an awesome and fun story/game. Perspective, really.

But I have deep, abiding love for our good old friend Tome of Magic, especially the Binder section, which has absolutely awesome flavor, and just ends up generating a ton of ideas.

Also, Die unendliche Geschichte, for our German readers  .

[Pimpforged]

I'm fond of The Black Company Campaign Setting by Green Ronin

[Avehn]

Nobilis - I had trouble with the game itself, it was too, vague and open, I guess, there weren't enough rules and I never knew what I was supposed to be doing, but I've gone back to that book over and over for the heraldry creation stuff and for making deities to incorporate into other settings or even novels.

[Jrussell82]

All the books I've seen for Scion by White Wolf have been fantastic in terms of the balance between fluff and crunch.  The fact that the idea that your character eventually does become a literal god with consummate powers of "I do XYZ" and how it gets represented mechanically are fantastic.

[heroicraptor]

The Warhammer Fantasy books are bursting with flavored fluff.