What is the best endgame book on the market? I am looking for a book that is clear and covers every endgame that one should know to become a master. I am rated 1645 USCF. Please leave your recommendations below! 

silman's complete endgame course

Agreed...definitely Silman's book. Very well written. Easy to understand. Covers a wide variety of practical endgames.

Oops, I accidentally posted the same thing twice 

That book by Silman is well written. But don't restrict yourself on what you want to study on that book. As you see, Silman puts a rating restricion on what you should study on his endgame book.

I personally recommend Silman's Endgame manual as I own it too and it has a very systematic mating and endgame patterns for each class players.

Howell's Essential Chess Endings is excellent.

Out of print and, depending on when you look, it can be very expensive on Amazon.  It's pretty clear that Silman "borrowed" from this book when doing his own endgame manual.

I think the Howell book is better overall, especially since it contains good explanations and exercises.  

I don't know that there is agreement about "every endgame that one should know to become a master", but I suppose that two natural book-candidates are Dvoretsky's Endgame Manual by Mark Dvoretsky

https://web.archive.org/web/20140708233815/http://www.chesscafe.com/text/review399.pdf

and Fundamental Chess Endings by Müller and Lamprecht.

http://seagaard.dk/review/eng/bo_endgame/ga_fundamental_chess_endings.asp?KATID=BO&ProductID=104&PUBID=GA&AUTID=69&BUYID=&ID=BO-Endgame

Fundamental Chess Endings is really good.

Plus this book looks promising, I stumbled across it tonight. "100 Endgames You Must Know: Vital Lessons for Every Chess Player" by Jesus de la Villa

There is an edition that was released earlier this year. So don't get suckered into paying for the older out of print versions.

Understanding Chess Endgames by Nunn is also very good.

http://www.amazon.com/Understanding-Chess-Endgames-John-Nunn/dp/1906454116