Winning on the Wind - Used
by George B. Moffat Jr. 
This book is no longer in print.  Below are links to used copies.
Paperback, 243 pages, many black and white photos and line drawings
Dimensions: 5.2 x 8.2 x 0.55 inches (132 x 208 x 14 mm), Copyright: 1974

This is a classic book about the technical and psychological aspects of flying fast in sailplanes.  It also includes interesting notes on gliders of the period. 

Search for used copies at: alibris or amazon.com or ebay