If you’re looking for a book about Sierra On-Line I’d recommend High Score. It had a industry wide focus but there was an extensive Sierra On-Line section. It looks to be ‘out of print’ but there are several used copies on Amazon.
The book was co-authored by Johnny Wilson who was the editor of Computer Gaming World when it was still a computer games magazine (and, you know, still existed). I’ve seen Wilson mentioned here and there as a ‘friend’ of Sierra On-Line during the early days and the Sierra section does have a inside feel to it. If you haven’t already, check it out.