Good question. That era is definitely under-represented in books.
Booker T, Regal, and Dustin all have books, but I can't remember how much focus there is on pre-Nitro WCW. Dustin, in particular, seems to rush through his career.
As for a book focusing solely on that specific era, there isn't one that I know of.
Of course, there's the Nitro book, but that is the opposite of what you're asking for.