I would also recommend "Walk Away Rene’ " by Hipgnosis, written by Storm Thorgenson.
This is a sort of corporate history of the company, with extensive discussions of a lot of their album cover work, especially for Alan Parsons, Pink Floyd (they worked with the boys from the beginning), 10cc, Led Zeppelin (“Presence”), Paul McCartney (“Wings Over America”) and others. They discuss why some designs work and some don’t, with a goodly amount of technical detail. Lots of illustrations, lots of insight into the creative process.
That said, some of my favorite album cover / packages:
Goodbye Yellow Brick Road and Captain Fantastic, particularly the comic book in the latter detailing the lads (John and Taupin’s) start.
The Police’s Spirits in the Material World is a good example of integrating music and visual images.
Sgt. Pepper is pretty iconic by now. I’ve got the New York Times Book review cover that did the same thing with the Clinton Administration. It’s a hoot.
Never Mind the Bollocks, Here’s the Sex Pistols is so much a part of its time that it should be a museum piece. Guaranteed to piss you off on so many levels, and you haven’t even played the album yet!
Loved London Calling and the Yes albums as well.
Rolling Stones Some Girls was a brilliant piece of art, even if you can’t really get what they’re about. Lynrd Synrd’s Street Survivors is creepy, considering the band crashed and burned as the album came out.
It’s a great pity that, for all the advantages of a CD, it killed album cover art.