ON BEING A BIRD and WHERE NO BIRDS FLY by Philip Wills are
among the best literature of gliding. There are plenty of excellent
basic primers for the student, but beyond that anyone aspiring to
experience the essence of unpowered flight needs to tap into what
the doyens of the gliding movement had to say on the subject.
Philip Aubrey Wills CBE, (26 May 1907—16 January 1978)
[ was a pioneering British glider pilot. He broke several gliding records and was the 1952 Open Class World Champion. He remained a regular member of the British Team until 1958. He was second in command of the Air Transport Auxillary during the Second World War. He was chairman of the British Gliding Association for 19 years and was awarded the CBE and the Lilienthal Gliding Medal for services to gliding. (from Wiki)
Ann Welch, HAPPY TO FLY, is another brilliant book, as is her ACCIDENTS HAPPEN.
There is review of some of the best books here -
Books for Glider Pilots