Extremely cheap good book
Porsche - The Legend
Jonathan Wood Porsche - The Legend
Don't be put off. Colour pictures of all models and some good detail with tables a la top trumps of information.
928 model coverage is good with pictures of UK cars from 1979, 1988 and 1995 although the author dismisses the 928 as a footnote in the companys evolution.
For a couple of quid its worth adding to your collection.