Most of us have come to understand the differences between performing routine maintenance and accessory installation, and chambering and fitting a new barrel. If you are standing in the midst of expensive machinery, and you know how to use the equipment with a quality result, you don't need this book. If you'd like to install your own scopes, recoil pads, replace small parts and tinker with a gun to improve its accuracy, you would probably find this book to be useful.
"Do-It-Yourself Gun Repair" is presented into five logical parts: An Approach to Gunsmithing in the Home Workshop, Basic Maintenance and Repair, Disassembly - Repair and Reassembly of Popular Firearms, Advanced Techniques, and The Final Steps. The book begins by showing ways of assessing if your firearms need work or maintenance, then it move on to a chapter dedicated to determining the scope of work that could reasonably attempted. There is a chapter presenting common and useful hand tools and a brief section covering frequently used power tools. The section that follows, which addresses the work area, special tools and parts supplies is pretty sketchy. A chapter titled "Thinking Like a Gunsmith" is thoughtful, but not substantial enough in content to assist someone in acting on some of the suggestions.
"Basic Maintenance" is more of a page filler. It mostly advises how to clean a firearm, something that could be found in many sources, including packaged in a cleaning kit. A follow on section covering analyzing and correcting accuracy problems is well written and, based on my own experience, would be very useful to almost anyone. "Ten Easy Gunsmithing Projects" is OK, but the projects are a little specialized and most lead to purchasing tools or material Brownells. The section isn't bad, I just believe there are more universal and common projects, and I am not taking a poke at Brownells. They are one of the best tool and material sources out there for us gun owners.
There is an excellent section regarding proper scope mounting that results in centered optics and proper hardware alignment, and included the proper use of shims under mounts for the purpose of leveling. This is an area so fundamental to good accuracy and frequently people don't take the time to perform this task correctly. The section on various firearm disassembly and assembly is actually very good. The author includes popular firearms, very good illustrations and photos, assembly tips, and coverage of common problem correction for each specific firearm.
Some of the information offered in other sections is not so directly useful. You are not going to learn how to checker from half a page of text and one picture of a checkering tool; artistic craft work takes a lot of talent and practice to master. There is an eight page chapter, chapter 23, dedicated to drilling and tapping a firearm for sights that is decently done, but you would need to purchase a $160 B Square Professional Drill Jig or a $400+ Foster Scope Mounting Jig to do the job, and you would have to possess the basic skills of drilling and tapping and how to properly set up fixtures. There is a good information addressing the repair of stocks and fitting a recoil pad, but they all presume prior woodworking and machine operating skills and the use of some specialized machinery and fixtures. Work of this types, to justify the cost of fixtures, needs to be a frequent requirement or it is easier and less expensive to drop the gun off with a good gunsmith. Still, it doesn't hurt to know what you are asking a gunsmith to accomplish when you purchase services.