"Silman's Complete Endgame Course" by Jeremy Silman
Endgame manuals typically cover "theoretical" endings with few pieces, those that had been previously fairly thoroughly analyzed by people (and now completely analyzed by computer in "tablebases"). They tend to be rather dull, but useful reading, as they do include a number of such endings that it is really important to know extremely well. What has always been lacking, until recently, is a book that covers only the most important endings to know, in a systematic manner. "Silman's Endgame Course" is that book. There has really never been anything quite like it, and it's a massive improvement over its only vaguely similar predecessor, the old "Chess Endgames: Essential Knowledge" by Yuri Averbakh. It's really the only endgame book anyone will ever really need, probably for years, or until they become about 2300 rated players.
Most of my study so far has been on openings and middle-game tactics, but my endgame play is subpar. Most endgame books I've found are devoted to rather specific endgames, or are pathetically loose in their coverage.
Can you recommend just a basic "cover-all" endgame manual I can start with, so I don't find myself caught out so easily?