Why yes, I did read the entire book from cover to cover. Real, dead tree paper, too. Ordered straight from the FSF website. It's a software manual. It's a good software manual. It's thorough. You will learn GDB if you read this book. You can skip a lot of the internals, API, and discussion about exotic hardware. But don't skip all of the internals - the "info symbol" and "info address" commands have been very helpful in assembly debugging. Oh, and I never would have tried writing GDB scripts if I hadn't read this.