The Emperor of All Maladies: A Biography of Cancer by Siddhartha Mukherjee
What was fascinating to me as a decidedly non-science person was the fact that though the term cancer is used broadly, the disease presents itself in a wide range of forms depending on where on the body it is affecting; and as a result, the types of treatments vary widely as well. What works to treat leukemia will not necessarily work to treat lung cancer, and vice versa; however, many examples are given where treatments for a particular cancer (especially leukemia) lead to research and discoveries of treatments for others.
In addition, Dr. Mukherjee provides some anecdotes about his patients and, with one of them specifically, he writes the story (spread throughout the book) almost like a novel where you really want to know how their story turns out.
No book about cancer can be without sadness and this one is no exception, but there are happy endings too and it is hopeful for future treatment and prevention.