Big Sur by John Kerouac

I am a Kerouac fan, so I may be a tad biased here.  I think this is an interesting look into Jack's mind -- it greatly shows his addiction and sliding mental state.  He was a literary genius who showed his true colours in a way many people would be afraid to divulge.
In this day and age of over sharing of one's successes or embarrassing moments, Kerouac was a pioneer of telling a tale of inner struggle and turmoil.  He is not self indulgent, and being true to his self a tad manic at times. It is an intriguing read that allows you to feel what Kerouac was feeling at this particular time in his life.
It is a quintessential read for Kerouac fans, and if you are a first timer, start with On the Road.