You will need a second book eventually. I'd recommend Muller's Secrets of Pawn Endings as your second, then Starting Out: Minor Pieces, The Survival Guide to Rook Endings, and Comprehensive Chess Endings Queen Endgame volume. Dvoretsky's Endgame Manual is also really good.
Studying endings.
There is a lot of topics on openings. I believe endings will teach more about chess. What is the best introduction to endings?
How to Play Chess Endings by Zonosko Borovosky
http://www.amazon.com/How-Play-Chess-Endings-Dover/dp/0486211703/ref=sr_1_1?ie=UTF8&qid=1386876890&sr=8-1&keywords=how+to+play+chess+endings
This book is inexpensive it has all the practical knowledge needed to conduct the endgame and the emphasis is on understanding principles rather than memorizing moves you can apply his techniques in any endgame situation you face. What he teaches will stick with you for life.
Also highly recommended is 1000 Rook Endings by Jozsef Pinter
http://www.newinchess.com/1000_Rook_Endings-p-1521.html
Beautiful book on Rook Endings.
There is a lot of topics on openings. I believe endings will teach more about chess. What is the best introduction to endings?