John Kennedy Toole - great novel. I have, on occasion, being threatened with legal action by pompous blowhards, and it always makes me think of Ignatius Reilly.
On a similarly sad note I just finished The Pale King by David Foster Wallace - his unfinished manuscript that he left on his desk after he hanged himself a few years back. Good Christ he was some writer - there's 4 or 5 passages in the book that are just staggering. The book as a whole is very unfinished, though, and quite difficult to work though. So not one to really pick up as a starting point to DFW.
He'd suffered from depression all his life but apparently had it relatively under control. His medication stopped working for him, though, and he couldn't find an alternative that didn't interfere with the creativity and energy he needed to write - committed suicide on that basis.
Thinking of picking up something by Denis Johnson next - been meaning to read him for ages but not gotten round to it. Jesus' son is prob his best known so may give that a whirl.