Let me start this one by saying: I'm not insane and I'm not a murderer...unless I really don't like you, then I'm going to kill you in an uniquely cruel way, and depending on how much I dislike you, I might do it in person or by poison...IN MY STORIES!
Geeze, not for real, guys!
Hold your horses.
As Castle once said: writers have the only job where they can get away with murder (without going to jail!).
Ah Castle...Oh Nathan Fillion, you complete me...
Back to the point. Here is another great reference book to keep on your nightstand for your late night writing endeavors. Also, keep it there when your significant other starts annoying you...it will give them a nice scare.
Deadly Doses: A Writer's Guide to Poisons, by Serita Deborah Stevens with Anne Klarnre.
The best part about this book is that it is classified by drug, symptoms, and affects. So, if you're looking for something that will affect the mind while not killing you...you get the picture.
Between having a book of poisons on the bedside shelf and a nurse or doctor on hand for those gory questions, you really can't go wrong.
I only ask one thing: DO NOT USE THIS BOOK FOR REAL-LIFE REVENGE OR HORROR PURPOSES!
It's a WRITER'S GUIDE!
Keep it to the pages...
P.S. The Howdunit Series has some other really amazing books to it for those who are on the lookout for resources for the creepy and the crawling and making your writing as true to life as it can be.