Alla Prima: Everything I Know About Painting THE best instructional painting book in the WHOLE WIDE WORLD! (as far as I know). This book is a MUST for any artist serious about painting well.
Problem Solving for Oil Painters: Recognizing What's Gone Wrong and How to Make it Right I've had this book in my studio for about 5 years now and I still refer to it for knowledge and inspiration. Highly recommended.
The New Drawing on the Right Side of the Brain This is the newer version of the book I used to learn to draw when I was a kid. Good painting comes from good drawing - this book is your gateway to that.
Painting Better Landscapes: Specific Ways to Improve Your Oils A great instructional book - filled with years of experience and wisdom. See her turn fairly average photos into great paintings.
Hensche on Painting (Dover Art Instruction) Profound colour and painting knowledge from a great impressionist/colourist painter. Priceless.
Painting the Impressionist Landscape: Lessons in Interpreting Light and Color Enjoyed this book for it's unique approach to seeing and painting colour. Griffel was a student of Hensche.
Sergei Bongart Great Russian impressionist. FULL of priceless knowledge - I literally couldn't put this book down. HIGHLY Recommended, but not for beginners.