Favorite endgame material
There are many good books.
A lot of people suggest De la Villa book on endgames. Winning Chess Endgames is written by Seirawan which in my opinion is a great player and chess teacher, look those 2 books up,they are great.
My favorite endgame material is two Queens!
As far as books go, I learned from the old Reuben Fine Endgame book and successfully taught people with it, so it's not bad.
I do have de la Villa's 1000 Endgames You Must Know and like the format of 9 Basic Endings, then 6 patterns of N and P Endings, etc.
I also have Silman's Complete Endgame Course from Beginner to Master and like the groupings by rating.
James Howell : Essential chess endings. Maybe wrong to call it my favourite as it's the only ending book I've ever looked at. It was brilliant though.
Various endgame study possibilities discussed at:
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
https://web.archive.org/web/20140708103149/http://www.chesscafe.com/text/review594.pdf
https://web.archive.org/web/20140708105702/http://www.chesscafe.com/text/review645.pdf
https://web.archive.org/web/20140708234309/http://www.chesscafe.com/text/review704.pdf
https://chessbookreviews.wordpress.com/tag/chess-endgames-for-kids/
Before buying any particular book, I suggest going to the publisher site to see if it is possible to view a sample.