The book briefly outlines Lovells early life and career as a test pilot up to the Gemini and Apollo programs, and the Apollo 8 mission before spending the bulk of the book recounting Apollo 13.
Even on the earlier missions and programs, the book is full of interesting tidbits, anecdotes and explanations. Particularly with Apollo 13 it is IMO quite gripping to read about the myriad of issues that came up and how they were discussed and dissected on the ground to systematically come up with a viable solution.
From the movie adaptation, I guess one of the more commonly know issues was the LiOH CO2 scrubber, where the CSM canisters didn't fit into the LEM. While apparently a lot less dramatic in real life, there were tons of other issues that the movie glossed over, from accidentally loosing navigation data while moving over from one computer to the other, the two course correction burns that were needed, exploding lead-acid batteries on the LEM, etc...
Anyway, as I said before, it's IMO a good read and I can strongly recommend the book.