I am increasingly using e-books rather than physical hard- or even paperbacks. They are easier to carry around (Usually the have an advantage in both volume and weight), and space is running out in my library. An excellent book that I am using at the moment is "Presidential Elections: Strategies and Structures of American Politics". This is now in its 13th Edition. It's original authors - Nelson Polsby and Aaron Wildavsky have passed away - but the quality and detail we had come to expect from them has been maintained. The Structure of the book is
Part One - The Strategic Environment
C1 - Voters
C2 - Groups
C3 - Rules and resources
Part Two - Sequences
C4 - The nomination process
C5 - The campaign
Part Three - Issues
C6 - Appraisals
C7 - American Parties and Democracy
If you need the physical version - further down the page is a link to the hard and paperback versions.