If you are looking for a medium level introduction to 2G, 3G and LTE then this is a great book authored by my friend, Martin.
This book doesn't go into the same minute detail as books that focus on each standard but it is a really useful overview of the different standards and how they work. This is a book that I still refer to when I need to remind myself how certain mobile comms functionaliy works.
P.S. If you are interested in understanding the capabilities of mobile comms at a user level then I can thoroughly recommend his blog (http://mobilesociety.typepad.com/).