The Art of the Start - Guy Kawasaki
Crossing The Chasm - Geoffrey Moore
Business Model Generation - Alex Osterwalder
The Personal MBA - Josh Kaufman
Blue Ocean Strategy - W. Chan Kim and Renée Mauborgne
Also, see:
http://www.quora.com/What-are-some-must-read-books-for-entre...
http://www.quora.com/Business-Books/What-business-books-must...
http://www.quora.com/What-are-3-books-you-would-suggest-any-...
and
http://personalmba.com/best-business-books/