His own biography (somewhat stilted writing, the constant "I" self-referrals, but, dense and very interesting):

My Inventions: The Autobiography of Nikola Tesla http://www.amazon.com/My-Inventions-Autobiography-Nikola-Tes...

He had his own vision of a "singularity" basically interconnectedness of all human kind across earth to "rid ourselves" of war. Free energy, etc. Held full models of his machines and ideas in his head (spatially fascinating) before construction.

Several nervous of mental breakdowns when over-working, strange debilitating flashes of light, etc. Probably some brain chemistry idiosyncrasies.

http://www.amazon.com/My-Inventions-Autobiography-Nikola-Tes... (no affiliate link, weirdly I always had trouble finding Nikola Tesla related books / documentaries (I believe documentaries are still only on youtube / amateur)).