I found several errors as I was reading it, although the only one I remember is that Peter seems to think that Jeff McCarthy was the original Beast in BATB (it was Terrance Mann)
Also, Peter has a disconcerting way of expressing opinions as fact. He declares that "Sunrise, Sunset" is the biggest hit to come out of a 60's musical...Because it's played often at weddings. That's the only evidence he offers. In his chapter on "The Producers", he mostly talks about the unsuccessful Toronto company, and then states that "no smash-hit musical fell from so high a perch to so low a rung in so short a time" (although the show ran 6 1/2 years, had two successful touring companies, and a London company that won the Olivier award for best musical)
Often, in his choices about what constitutes the biggest "hit" or "flop" in a certain year, he'll often make some strange choices, based on (I assume) which shows he wants to write about. For 1965-1966, he's decided that the biggest flop is a show called "Little World, Hello", a show that never even made it out of rehearsals. By that criterion, any show that's had workshops without making it into production ("Kicks" comes to mind, although there are many others) would somehow constitute the biggest flop of the year.
I enjoy Peter's columns, but this book reads like it was written in a hurry.
Behind the fake tinsel of Broadway is real tinsel.