Great product - I use it all the time, both in preparing for the game and at the table. Last session I used it to come up with a bunch of names and simple motivations for some "background NPCs" who were working on a merchant caravan with the PCs - the kinds of folks that they are unlikely to spend much time with, but if they do, you want something more than "Er, yeah, his name is, er, Thag, and he likes, er, fighting evil..."
I've used it at the table for example, when the PCs were in a tavern. I had the book open to the pages about tavern patrons. So when one player wanted to know what the dwarves at the next table were doing, I had their conversation material and motivations right there in front of me.
That's where it gets the most use - in whipping up random people and places at the drop of a hat. Names, locations, motivations - all that kind of thing. None of it is the sort of stuff that I couldn't come up with myself, but the book's main strength is as a timesaver - it's all right there for you when you need it. No DM can cover every possible NPC or angle beforehand, so I like having a resource that I can smoothly turn to an incorporate quickly and easily.
I get less use out of the encounter tables, mainly because they are 3.0. I'd love to see a 3.5 version of those lists (especially the people as opposed to the monsters) but there you go.
One player, after leafing through it, described it as "a campaign in pieces, waiting to be assembled". Good description - it really is all the component parts. Just add DM, stir gently and serve

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