Book #18:
"Tao Te Ching" by Lao Tse

"The Tao is one of the shortest books on philosopy of life ever written "

The best thing is the Tao doesnt tell you what to do. There are simply 80 or so small verses some no longer that a line or two, which could get you thinking for years. The idea however with the Tao is that you experience what they say as opposed just intellectually understand it, which I would say is the KEY to all personal development.

Have a read of this, there is such beauty in it's simplicity and truth.