Essential Chess Engames Explained Move by Move, by J. Silman
Chess Endings, Essential Knowledge, by Y. Averbakh.
Indeed, lots of good endgame books are available. GM John Nunn's many books are recommended --
http://www.amazon.com/Understanding-Chess-Endgames-John-Nunn/dp/1906454116

I would be interested to know what the forum considers to be the absolute essential endgame knowledge for a club player. I have read on this site that some consider it to be around 200 positions (Dvoretsky?) while books I have read state that its around two dozen (Andrew Soltis)