The only band-authorized "official" bio was Samuel Graham's
Authorized History of Fleetwood Mac, but that's primarily a marketing artifact.
The band's very first, interim bassist, Bob Brunning, also wrote a couple of
books.
Ken Caillat's
book on the studio experience is I'm sure authoritative.
The best thing any fan can do is to plow through the Penguin's Blue Letter Archives right here.