I wonder if Wambaugh wrote his book partly in reaction to the "Adam-12" show.
As a kid watching those shows, it was easy to think that those clean-cut characters reflected how every cop was and that being a cop was one of the best jobs in the world to have. So what a shock it was to me, as a 13-year-old kid bicycling through a road work sign to have a big-bellied cop working the detail step in front of me with an ugly expression and bellow "move the hell outta my construction area ya punk or I'll take that bike and shove it up your ass!" while the road crew leaned on their shovels and laughed at my shocked "deer-in-the-headlights" expression. I hightailed it out of there and never looked back.
Of course, not all cops are that way. But that incident was the beginning of my realization that the real world did not resemble in the slightest those antiseptic TV dramas and sitcoms. Speaking of my childhood naivety, as a 10-year-old, I actually wrote a letter to the Partridge Family asking them if they needed somebody to help out with the band - even properly addressed it to "Reuben Kincaid, manager". Yes, one of my childhood fantasies was apparently to be some sort of "roadie" for the Partridge Family! But I digress.
I happen to know a police officer pretty well, he's married to my cousin. I'll have to bring this book up next time I see to him. He's probably familiar with it. He talks to me about police work sometimes and a lot of what he told me about it comes out in the book, such as the impression many officers have that they are sometimes "shoveling crap against the wind." That is to say, dealing with the same drunks and bums night after night, only to see them right back on the streets hours later.