This is really fascinating. What an interesting mind and outlook that man had. Sure it isn't considered 'normal', but what is these days? A lot of famous people, artists, writers, musicians and so on, were considered either 'a bit nuts' (public opinion) or were actually insane/mentally unstable (medical diagnosis). Yet they're famous not from their mental state but from the work(s) they produced. I'm not saying that this man's work should/should not be put in a museum or whatever (haven't had a chance to read it properly, hoping to though), but what he wrote should not be immediately discounted just because he wasn't mentally stable or because he was justifying his suicide.
Long story short: Don't discredit his work because he's considered crazy.
Long story short: Don't discredit his work because he's considered crazy.