What's the best and worst D&D book you own from any edition?

I was looking at my bookshelf of D&D books (2E, 3.xE and Pathfinder) and thinking about how "good" or "bad" some of the books I owned were. Heck, several of them I'm not sure I've even done more than flicked through the pages once.

So I'm interested in seeing what everyone regards as their "best" and "worst" D&D book in their collection. The book(s) can be made by TSR, WotC or Paizo or they can be a 3rd-party product. It can also be from any edition. It just has to be one you own.

Best and worst are entirely subjective. You may decide your best book is the one that you got the most value for money from (i.e. your PHB that you've used to get over 1000 hours of gaming out of) or it may be the book you enjoy looking at the most, even if you don't use it much.

Similarly, your worst book may be one that you found all the rules within it to be horribly broken, a book that you horribly overpaid for, or a book that had fluff that ruined for a particular setting or character for you.

For me, the best D&D book I own is the Shackled City Adventure Path by Paizo (3.5E). It's my best D&D book because with it I ran a campaign for over 3 years and about 100 sessions, starting at 1st level and ending at about 18th-19th level. It was the longest campaign I've ever DM'd and the only one that reached the end point I'd hoped for at the start of the campaign. Yeah, I changed and added many things in the adventure (including a full re-write of the final adventure), but I definitely couldn't have come up with a campaign half as cool by myself.

Normally I'm complete bibliophile with my books. I hate to write in them at all or get them damaged. Almost all my RPG books are in pristine condition. By the end of the campaign, my SCAP hardcover was completely trashed. The front and back covers the book spine were all damaged. That wasn't because the book was poorly made. It was simply due to how much time the book spent in my bag as I took it to and from work to read on the train or on my lunch break. The book earned it's keep and then some.

The worst D&D book I own would be the Epic Level Handbook by WotC (3.0E). This is because of a couple of reasons.

Firstly, I paid around $80-$90 AUD (about $75-$80 USD on current exchange rates) for the book. A combination of no knowing about buying books online and a very low AUD exchange rate meant I paid a lot more for the book than I should have.

Secondly, I've never had a PC reach 20th level, or ran a campaign where the PC's have. So I've never used anything from the book in-game. I read through the book a little when I bought it, but haven't cracked the cover in 5+ years.

Thirdly, having now run quite a bit of D&D 3.5E at Level 15+, I've discovered that it's not anywhere near as fun to run as it seems. There are that many spells, magic items, abilities and effects in play that it's not much fun to keep track of as a DM. So I don't think I'd enjoy running an epic level campaign. So the book just won't be of any use to me in the future.

So that's my best and worst D&D book that I own. What's yours?

Whoops, this should be in the D&D and Pathfinder forum. Mods feel free to move.

Best:
Probably Unearthed Arcana (3e). This is really what D&D is about: taking the published game and making it yours. Taking the variations and sharing them through the OGL. Every book should have looked more like UA.

Worst:
Probably Return to the Temple of Elemental Evil. I'm cheating a bit since this is an adventure and not a rulebook (OP didn't specify) and I'd likely say the same about any other adventure, but I received it as a gift and it just seems like some sort of cruel joke that as a DM I would be expected to use this instead of my own ideas.

There are some mediocre ones and some with very mixed ideas or poor editing, but I can't think of any rulebooks I have that disgust me on the same level.

Ahnehnois, there's no restrictions on the type of book. It could be a core rulebook, a splatbook, a monster book, adventure, whatever. I chose an adventure as my best book so RttToEE is a perfectly fine choice as a worst book.

Best: <EDIT - oops, D&D> D&D Moldvay Red Box set. It's the D&D I started with. I still love to play it to this day.

Worst (that I still own): Cardmaster (for AD&D 2E). It was a product that came out during the era of the likes of Heroquest and Warhammer Quest and computer games like Dungeon Hack (those three were good, Cardmaster is not). It's a boxed set full of thin, cheesy dungeon cards and a "monster" deck. Mostly designed for solo random dungeon play. Utterly boring, thrown-together ruleset. I'm not sure why I haven't purged it from my bookshelf.

P.S.: Epic handbook is pretty up there for worthless for me for the same reasons. It's a shame I was a completionist back then; I bought the autographed version (mainly for the Olidamara dice).

Best is probably the "Campaign Sourcebook and Catacomb Guide" for 2nd Edition. That book probably taught me more about DMing than any other source.

Worst is a bit trickier... The "Epic Level Handbook" is pretty bad, as is "Deities & Demigods" (3e version). Indeed, the two together are shockingly bad - in order to really use the deity stats you need epic level PCs, but the ELH uses a largely-incompatible system for such powerful characters! "The Book of Exalted Deeds" is also remarkably poor.

But I think the worst is probably "Scourge of the Howling Horde". It's an incredibly dull, railroady adventure, pretty much every stat-block is wrong (including several monsters drawn unchanged from the "Monster Manual"). But worst of all, it was clearly typeset assuming full colour, and then printed in greyscale, with the net result that several of the sidebars are nigh-unreadable.

Best: Aurora's Whole Realms Catalog. 2E-era but really setting and edition independent; it's just a really fun flavorful book.

Worst: Toss up between Epic Level Handbook and Book of Vile Darkness.

Best: Realm of Terror, ravenloft boxed set

worst: the 3.5 Expidition to Castle Ravenloft Adventure. The original Ravenloft module was amazing, this new version was awful, basically caused me to stop buying WOTc products for the remainder of the 3.5 run. Just reduced a cool setting and adventure to something that felt more like a video game.

Best Book? It depends.
Rules: Unearthed Arcana
Class (3e): Psychic's Handbook (Green Ronin), Shaman's Handbook(Green Ronin), or Witch's Handbook(Green Ronin)
Class (2e): Complete Thief's Handbook
Class (1e): Witches (Mayfair Games)
Setting: Dark Sun or Al Quadim: Land of Fate
Monster related: Advanced Bestiary (Green Ronin) or Book of Templates (Silverthorne/Goodman Games)

Worst Book? I am not sure. I pared down my pre-3e books, avoided most 3e WOTC supplement like the plague, and was selective about third party supplements that I purchased. My worst supplement is probably, one of the free pdfs that I picked up on RPGNow or, maybe, B2: Keep on the Borderlands (not a fan of the caves themselves)

The best is Rules Cyclopedia. It has everything one needs in one book and the rules and game work great.

Worst if I'm including 3rd party books then some of the FFE and Mongoose books were just terrible in the age of d20 bloat. For actual D&D books I have to go with WG7 Castle Greyhawk. After waiting for it and hoping it would be some awesome epic module we get a very bad parody comical thing that failed to be funny.