I just purchased Poisoncraft: the dark art from Blue Devil Games, and I'm decently impressed so far. Haven't read it all yet, mainly just the poison creation rules and then skimmed the rest. It is the first non-wizards source material I've bought for d20, but I like it. I'd been playing around with the idea of a poisoner character for like a year now, but I never quite got it to come together for several reasons: 1) poison sucks. the DC's are generally just to low to be effective when you get to higher levels 2) exisiting classes, like the poisoner prestige class in dragon magazine, are retarded. poison gaze attacks? c'mon. 3) trying to make my own prestige class proved very, very difficult due to the very complicated nature of determining the cost and difficulty of crafting new poisons. We are never given a formula for crafting poisons in any DnD sourcebook, but this one gives you a way to craft anything. Really. They take into account DC to resist, ability damage dice, special effects (all the "status ailments" listed in the core books but aren't ever suggested as poison effects, for example, blindness or nausea), uber special effects (decreasing spell resistance, natural armor, ability to wild shape, and other cool stuff) duration, delivery method, and more.
In many ways, the book makes poison much more powerful because it allows for more options for customization (like increasing the toxicity--the DC to resist--or making poisons that penetrate racial poison immunities. oozes beware, heh). On the other hand, it makes poison weaker because by expanding poison rules, they also introduce new limitations that were assumed not to be there before. For example, they group poisons into families. If a poisoner wants to make a poison, they have to "know" the family. They can learn a family by studying a poison from that family (decently difficult poisoncraft check) or for every 3 ranks put into the poisoncraft skill they learn a new family. There are also some rules that make a lot of sense, but I'm not a huge fan of (mainly because of the complication it could add to the DM's job). For example, instead of just having a 5% chance to accidentally poison yourself when handling poison, you have to make an exposure check. However, this could get complicated because you now have to know the DC to create the poison in question; the exposure dc is based off that. And DC's to create are straightforwared, but as I have said, there are a lot of factors involved, so it can get complicated.
Generally, the rules seem very solid. Very balanced. I noticed a few discrepancies between 3.0 and 3.5, but nothing that seemed problematic. Really I just noticed they said wildnerness lore in one spot, and then survival in another. Reasonably interchangeable in this instance.
Now, I bought this book for $6.66 (not kidding, yes that's a bit creepy) from rpgnow.com as a pdf file. This is a 96 page book on poison. That's it. Granted, it is really very comprehensive when it comes to poison, but this isn't something that every gamer will want. As I said, I've been toying around with the idea of a poisoner character for a while, so this was perfect for me.
Anyway, I was pleased, and seeing as this was my first foray into non-wizards stuff, I wanted to share. If your interested, google for some other reviews, there's plenty out there.
Happy holidays, everyone!