Even if your marriage is great, this book has an excellent section on warning signs of future abuse- a MUST READ for parents and their soon to be dating children! This book also does a great job of helping support people better understand and support the abused partner.
Also read Lundy Bancroft's "Daily Wisdom for Why Does He Do That?" This book has daily bite-sized nuggets of wisdom and it is probably the easier read.
All the books I have read by Lundy Bancroft are great. He specializes in partner abuse- he's worked extensively with thousands of abusers and he knows their games. Expect his books to blow your mind with insight. He boils down all the controlling, manipulation, selfish entitled partner's antics (including cheating of course) and leaves the injured spouse with gold nuggets of clarity and empowerment. He also wrote an entire book on how to decide whether or not to stay in a relationship.
Seriously, do yourself a favor and read Lundy Bancroft.