Encyclopaedia of Chess Endings I - Pawn Endings - ECE I (2nd edition)

Lots and lots of examples, easy to study

The encyclopedia is much more extensive than any textbook on the subject. As it only contains the variations and requires the reader to infer the general advice and rules himself, it does require more thinking by the reader and is certainly not for the beginner. But for any player rated appr. 1700 or better, it is a fantastic source which few players will ever be able to exhaust.