Porsche built their reputation in the 911, a largely handbuilt, rear-engined model, but in order to survive the economics of the 1970s the company needed a model to reach the larger market. The 924 and the 944 were manufactured at the Audi works and were produced to fill this role.
The history and specs for the 924 and 944 is fairly detailed up to 1989. Some details for the S2 (1990-1991) are somewhat sketchy as the book was published in '89. If you're thinking of buying, the book provides great info about what problems the various models and years exhibited, as well as what to investigate closely, depending upon model and year.
The pictures are nearly all in black and white, but even the rare models are detailed, with photos included.
The appendices are particularly interesting (for example, showing you how to decipher the Porsche serial numbers).
