I like a good book as much as the next guy. If you are a runner, and do any reading at all, you have to read the books below. These are easily the best books I have ever read on running. All of them inspire in different ways and all are easy reads. Three of them I have actually read twice. As I look at the list, I think I am going to read another one of them for a second time as well.
I find this gross time of year (I am a hot weather runner) miserable so I need inspiration right now as much as anyone. I have linked them all to the amazon page for each simply so you have an easy avenue for information on the book, not to tell you where to buy it. In fact, if I were you, I would go the library route. It's free! The books are listed in no particular order.
The Long Run, by Charlie Butler and Matt Long
My Life on the Run, by Bart Yasso
Running with the Buffaloes, by Chris Lear
Ultramarathon Man, by Dean Karnazes
Once a Runner, by John L. Parker Jr.