yes, Proakis' boks were good but if you want the beginners approach use Communications Electronics by Frenzel (very useful) or Electronic Communications Systems by Kennedy
B.P.Lathi books are best plus i have used Skalr book sometime not efficient if don't knw basic.. but i recommand start with B.P.Lathi analog and digital communicaiton
Proakis, John G. Digital Communications
Glover, Ian Digital Communications
Das, J. Principles of Digital Communication
Ziemer, Rodger E. Introduction to digital communication
Added after 2 minutes:
I forgot a very good book 2 strt with.. Dtopics r simplified..
Haykin, Simon --- Digital Communications