Heres one I read via a recomendation on this site
Crawlspace
Im allways down for runaway/feral children stories.
First non-fiction?
It's about a culture of the homelessness underneath the early 90's NYC streets.
Really awesome read that I recomend through and through.
A documentary was made (equal in awsomeness)with a lot of the same characters in the book. The soundtrack is all Dj Shadow and the entire film is in black and white.
Tunnel People
Watch for free on youtube:
Dark Days Documentary