Various endgame study possibilities discussed at:
https://web.archive.org/web/20140708103149/http://www.chesscafe.com/text/review594.pdf
https://www.silmanjamespress.com/shop/chess/silmans-complete-endgame-course/
https://chessbookreviews.wordpress.com/tag/chess-endgames-for-kids/
http://www.gambitbooks.com/pdfs/Chess_Endgames_for_Kids.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/7742.pdf
https://www.chess.com/article/view/book-review-winning-chess-endings
https://web.archive.org/web/20140708105702/http://www.chesscafe.com/text/review645.pdf
http://www.jeremysilman.com/shop/pc/100-Endgames-You-Must-Know-78p3863.htm
https://www.newinchess.com/media/wysiwyg/product_pdf/9026.pdf
http://chessimprover.com/averbakhs-chess-endings-essential-knowledge/
https://web.archive.org/web/20140708101138/http://www.chesscafe.com/text/review373.pdf
https://web.archive.org/web/20140708234309/http://www.chesscafe.com/text/review704.pdf
http://www.gambitbooks.com/pdfs/Understanding_Chess_Endgames.pdf
http://theweekinchess.com/john-watson-reviews/endings-endings-endings
http://theweekinchess.com/john-watson-reviews/the-end-game-comes-before-we-know-it
http://theweekinchess.com/john-watson-reviews/theres-an-end-to-it-all
Before buying any particular book, I suggest going to the publisher site to see if it is possible to view a sample.
What is a best way to improve endgame play?