Locard's Exchange Principle: "Every contact leaves a trace." And that is the standard principle upon which all forensic science is based.
And, this book, does, in fact, cover the history of forensic science, as far back as bertillonage (anthropometry), the development of firearms and gunpowder (leading to ballistics) dactyloscopy (fingerprint analysis) and trace evidence up to modern day techniques such as spectroscopic analysis, DNA fingerprinting, and facial reconstruction.
And, although the book is interesting as a history text, the "often gruesome and always fascinating" part does not belong in the title, at least in my opinion. the book appeared to discuss more about the people--the police, the detectives, the scientists, and how they solved the actual crimes.
A brief outtake: "...this case was solved by another extraordinary forensic scientist, Professor John Glaister, Jr (1892-1971). During the First World War, Glaister served in Palestine with the Royal Army Medical Corps before returning home in Glasgow in 1919. There he became an assistant in Glasgow University's Dept of Forensic Medicine where his father (...also a prestigious forensic scientist ) was regius professior. ... Glaister Jr. spent 3 years in Cairo as a professor of forensic medicine at the University of Egypt where he had the unique opportunity to examine mummified bodies. He succeeded his father as regius professor in 1931..." and so on it goes.
If you are interested in the historical life story of some of the detectives, and how some of the forensic items came into use, then this book is for you. There are some gory details discussed about certain crime scenes, but I found the book to be quite lacking.