No one has yet mentioned Endgame Strategy by Shereshevsky. It is more about the mindset you need to play endings well than endgame theory, but does have plenty of interesting positions and analysis as well.
There are many more good endgame books that have not been mentioned.
Pachman wrote a good one (Chess Endings for the Practical Player) that does not intimidate you with masses of standard positions and an encyclopaedic style.
Reinfeld's books (Instructive and Practical Endings From Master Chess, Practical Endgame Play )
Jonathan Hawkins (Amateur to IM) re-inforces the importance of studying endings through the example of of his own relatively late development (FM at 25, GM at 31) and shows you the right way to study the endgame.
DVORETSKY'S ENDGAME MANUAL AND SILMAN'S COMPLETE ENDGAME COURSE ARE OUTSTANDING BOOKS
I am currently studying this Silman's book. Amazing !