"En Route" by Kelly Grayson has been renamed "A Paramedic's Story: Life, Death, and Everything in Between". It's definitely the best of the EMS books that I've read in its scope, relevance, and mix of gravitas and humor. In my experience, it does the best job of capturing the day-to-day feelings of the job. Plus, he still writes, for EMS WORLD magazine, so you don't have to worry about too much BS in his writing.
"Paramedic! On the Front Lines of Medicine" by Peter Canning is a decent read, but there's nothing really memorable about his experiences or his writing, except that it was interesting to see someone go from being deeply involved in Washington politics to responding to 911 calls in early 90s Hartford. The politics and the personal reactions are just that, personal, so try not to get frustrated with them. "Paramedic!", isn't a throw-away, necessarily, but I felt like Canning had something meaningful he was trying to say but lacked the skill in prose to tie it all together.
"EMS: The Job of Your Life" by Devin Kerins is forgettable, just like most of the back-of-the-truck stories that you've heard, because that's exactly what it is. This book is probably great for the station coffee table or john, but it is by no means a deep and introspective look at the world of EMS.
A book that's a little out of the way, but was recommended to me by physician, is a little novella called "Black Flies" by Shannon Burke. It has no chapters, and you can read it in a day (think "Of Mice and Men" length), but it is a great read and an intensely written account of a first-year medic in Harlem in the early 1990s.
My advice is to buy both "A Paramedic's Story" and "Black Flies" and enjoy them both. They're strikingly different styles and stories, but I enjoyed both of them immensely.
(ps) All of these I bought through Amazon. Most are available in Kindle format, but you'll have to check for specifics.