It's maybe 20 printed pages, and there's nothing in here we don't already know. He basically chronicles everybody else's work. This just an over-view, doesn't mean it's not informative, though.
Martin's writing is primarily a open-source intelligence (OSINT) project. He aggregates and accumulates a vast amount of articles that have been written by others, and cites them religiously throughout. He intersperses his own brief analysis and thoughts in the writing, but adds little new or original.
There are several things that I feel are not fully fleshed out and addressed in the book, which keep me from giving it 5 stars. Organization, training, equipment, and quality of life for families and operators are all topics on which the reader will not learn much new. All these are topics which can be touched upon without revealing tactics, techniques, or procedures (TTP's) that would place operators in danger. Everything Martin uses has been previously published, and so he does not tread new ground in anything he covers. However, his analysis is missing in exploring deeper on what this can mean, and what people should take away from it. With writers like Dalton Fury using their own background in SMU's to bring out books, and Navy SEAL's once again flooding the market with their own propaganda, there are resources out there that a journalist like Martin can reach to tap into. This project appears to have occured entirely behind a screen.
However, he does a great job of outlining how Delta has influenced American policy choices, and how the unit leads the army in development of TTP's. He goes through the development of the industrial killing machine that decapitated the Iraqi insurgency, and then turned its focus towards Afghanistan and beyond. He does a great job of teasing out what may or may not have happened on several recent missions attributed to the unit, and spends a bit of time looking forward. Overall, this is a tremendous effort in collecting information, vetting it, and then editing it together with some analysis to produce a concise history of a unit that avoids the limelight at all costs.