"The Complete Manual of Suicide" by Tsurumi Wataru. It details various methods for committing suicide, sorted by category and annotated with failure rates. All of these are accompanied by scientific and graphic descriptions detailing each method, including case studies of successful and failed attempts. Probably not bedtime reading material for most people.
This is one of those "considered harmful" books due to its contents, so it used to be really hard to get, but these days you can easily buy a copy from Amazon Japan. I wouldn't say this book is particularly harmful as it does not encourage suicide in any way. Instead, I find it to be a fascinating book about various breaking points of human, and knowing these limits are pretty useful in life.
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