A man named Bill Soto-Castellanos, who served as a batboy and clubbie for the San Francisco Seals back in the 50s, has written a book about the late, great Pacific Coast League called 16th & Bryant: My Life & Education with the San Francisco Seals, I haven't read it yet, but a review can be found here.
I say "late great" because the PCL that exists today is not the PCL as it existed before the Dodgers and Giants invaded the west in 1958. In those days the PCL was pretty damn close to a third major league. Actually was one for people west of St. Louis. The accounts I have read claim that the quality of play in the golden age PCL was outrageously high. Even better: because of the favorable weather, the old PCL had a crazy-long season, lasting as many as 200 games over nine or ten months. If that happened today -- and it were televised -- I would almost certainly be divorced by now.
Based on the review, Soto-Castellanos' book does not appear to be anything like a comprehensive history of the PCL (you may want to check out another book for that), but I have often found that I get more out of a personal perspective like this one than I do from a top-down history.