Generally, this is a pretty good factual book. It's mainly a third person account of events, but with interspersed transcripts of interviews with the men who were there. There are 18 chapters in the book (plus a brief prologue and epilogue). The first twelve chapters are devoted to the formation of, and operations of, various British special forces units during World War 2. There is one short chapter on the immediate post-war period, two about the Korean War, one about operations in Egypt around the Suez Canal, one about the Falklands Conflict and one about more recent operations (mainly in Northern Island, but with mentions of other). This might be a bias towards the early history of these units, but there was obviously a lot of action then, so maybe that's fair.
The book covers the original Army commando units, as well as the Royal Marine units from later in World War 2 up to the First Gulf War (briefly). There is also some discussion of other special forces units, including the famous SAS and SBS as well as less well know specialised raiding and recon units. There is a lot of interesting information in the book without it becoming bogged down in details, with a good mixture of high level description, unit actions and personal accounts.