Books sitting and collecting dust because they were just THAT bad or disappointing:
Ravenloft Campaign Setting. Knowing just how amazing White Wolf is with horror in the medieval, I was positive that this book would be amazing. It was quite boring instead.
Book of Eldritch Might. I believe Cook was one of the first big-names from WotC to do his own thing (at least it was the first I noticed). When I saw corebooks heading a bit more towards the powergamer side, I figured He was doing his own thing to get back away from the powergamey stuff. Oops.
Books that are great but are unfortunately collecting dust:
Spycraft and Stargate SG-1. Amazing books with a surprisingly versitile setting to work with, but I have been playing D&D for far too long. It is very easy for me to come up with a variety of aspects of stories, NPCs, red herrings, etc when working with a fantasy setting because it is what I have been playing for far longer than I care to admit. I honestly have not had the time or desire to put the work into these two games that would be required to run one of these two games at the quality I expect out of myself.
Swashbuckling Adventures. I hoped to be able to incorporate some of this information into my D&D game, but felt that a lot of it would be "lost" when taken out of the setting. Additionally, many of the mechanics do not work as well (read: are too powerful) in a "normal" D&D setting. However, I really hope to find a time when I could devote a game to an all-Theah game.
Books that have been surprisingly useful:
AEG's Toolbox. This was sorta an impulse purchase when I had some store credit at the FLGS and nothing else was out at the time. At first I thought the myriad of tables would be helpful, but I find myself using the many ideas and tables in a non-random fashion; more for inspiration than anything else.
Kingdoms of Kalamar and its Atlas. Only an extremely tiny amount of space was wasted on mechanics, magic, or anything that did not specifically support the game world, its history, and how players function within it. At first, I expected a decent setting with some nice detail (at a discounted price which is what convinced me to buy them), but it has provided me with a superbly detailed setting with which to modify or use as I see fit (also according to the amount of time I have to prepare my games).
Notably absent from any of these lists are WotC products. These days (the Hasbro-era of D&D), it is fairly easy to peg what any given book will contain: Mechanics, stats, crunchy bits, and even more mechanics. I love them for that; I know I can get the rules I need or want from them and go to 3rd parties for the deep, important stuff like settings and story ideas.
Bought it, read it, and was left quite flat and disappointed by it's... same ol' same ol' ness.
