There is only one book I would recommend:
Title: Philosophical Essay on Probabilities
Author: Pierre Simon Marquis de Laplace
Year: 1794 (and still applicable)
Amazon Search: http://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias%3D...
Google Books: http://books.google.com/books/about/A_philosophical_essay_on...
Sure you can find more current texts, but this introduces it as if this was a cold introduction, and makes the foundation understanding almost complete. It's a pretty stunning piece of work, the essay being a popular introduction and not the underlying mathematical lecture it was based on.