Now don't be thrown by all the medals on this book. I know that it used to be in elementary school that you had to read a Newbery winning book like Johnny Tremain or something of that ilk and it was usually deadly boring. That is not the case anymore. The committees who decide on these things are usually comprised of librarians (wonderful, wonderful people!) who actually want you to read books you like rather than books that are good for you. And sometimes they run across a book that is both.
Now I can say in all honesty that An American Plague is gross. It is about disease and death and mosquitoes and smelly seaports. I had my face scrunched up into an unpleasant moue the whole time I was reading it. (And I know I am kind of showing off by using the word moue, but do you know how often you get to use that word? Almost never!) But it is a fascinating look at how an entire city was brought low by a tiny germ. The thing that amazed me most about this book is that it drives home the fact that anyone who has passed high school biology has more actually medical knowledge than the doctors who were trying to fight this plague.
Now if you like your facts wrapped around a story you simply must read Fever 1793 by Laurie Halse Anderson. Also The Pox Party: The Astonishing Life of Octavian Nothing Traitor to the Nation by M.T. Anderson is a simply magnificent and fascinating books that really shows how backwards scientific research was at that point in time. (Of course I wonder if people in 200 years are going to look at our medical practices and call us savages!) And finally an oldie but a goodie - Steven King's The Stand is the granddaddy of all plague books. It is about a thousand pages (you can build your upper body strength by lifting it as you read!) but you will get sucked in right away. I reread it every summer for about 15 years.
If you just like a true plague book, try Flu by Gina Kolata. It is a straightforward story of the 1918 influenza epidemic - well written and understandable.