My first reaction was that this thin little book was not going to compare with the thick and very comprehensive Police Procedure & Investigation, A Guide for Writers, by Lee Lofland but digging into the pages of the O'Byrne it appears very useful if you want to understand English police procedures.
Neither of these is the sort of book one sits down and reads like a novel, they are reference books although written in very different styles.
The Lofland is a much more detailed book in a serious textbook style with full explanations about the American system of policing covering everything from autopsies to prisons.
The O'Byrne is very much more a short fact packed short guide, and his writing style is geared to a British readership with phrases like:
"They cannot do a Paxman and ask the same question nineteen times....".
And "a bit like Top Gear without Jeremy Clarkson's subtlety and political correctness."
Michael O'Byrne gives us an honest picture of what a former senior officer thinks about some of his colleagues.
"Of course the shift is the home of the 'canteen cowboy', who has been everywhere, seen everything, done everything, but no one can remember when he last made a decent crime arrest."
CID ...tends to reflect the cynical edge of policing, and detectives still tend to have the poorest marriage record and the biggest drink problems [when this gets too bad they are sent back to uniform].
And Lee Lofland is just as honest:
Police officers can be a vindictive group. Revenge is the word. Hurt one of their gang , or spew hateful words against the brethren, and see how long it takes to receive a speeding ticket or find your car in the police impound lot. There are rotten eggs in any profession-police agencies are no different.
I think both these books are a mine of valuable and interesting information for the writer [who probably has researched much of this before commencing to write] and the crime fiction aficionado.
However I wonder what level of readership the O'Byrne book is aimed at when he tells us "the fictional world that Brown [The Da Vinci Code] had created looked comical rather than mysterious" and "It has been known for lawyers to be in cahoots with the criminals they represent."
There is a great deal of valuable information within the pages of The Crime Writer's Guide to Police Practice, especially about forensics, profiling and British serial killers, but the reader just needs to switch off and ignore the odd colloquialism, or perhaps the publisher should have provided subtitles for non-British readers.
"Stop and search however remained a dog's dinner until the Police and Criminal Evidence Act 1984 [PACE]."
Lee Lofland's excellent website is here.