In 2010, the American Musicology Society (AMS) Popular Music Study Group started a representative bibliography of books on popular music: http://grove.ufl.edu/~amspop/bibliography.html

It is not a comprehensive list but does include a number of ground-breaking models and places to begin research in popular music.  The first part of the list is divided into the following categories: 

A. Overviews: Research Guides, Disciplinary Assessments, and Methodologies

B. Production: Industry, Media, Sound, Performance

C. Consumption: Audiences, Geographies, and Identity Politics

D. Genres

E. Histories

F. Biographies: Single-Artist Studies

The document is a “living” document and therefore anyone can write to the Group to suggest adding new material.

From this list, I have recently read:

Spicer, Mark and John Covach. Sounding Out Pop: Analytical Essays in Popular Music. Ann Arbor: University of Michigan Press, 2010.

This collection of articles contains several excellent analytical approaches to popular music in particular those exploring the compositional processes of Leiber & Stoller and the Coasters, Roy Orbison, Marvin Gaye and the Police.

Zak, Albin J. III. I Don’t Sound Like Nobody: Remaking Music in 1950s. Ann Arbor: University of Michigan Press, 2010.

This work looks at the “sound of [the] genesis” [Introduction, p. 7] of rock and roll by reviewing the range of musical experimentation and technological change in popular music of the fifties.