We haven't really seen any books in English at all about our mountains. In Spanish we found just one:

"Disfrutar caminando por las Sierras Blanca y Canucha" by Victor Fernandez Martín.
Published by Editorial Arguval.
It gives a lot of information about trails to follow and it gives a good overview, from the geographic situation to the plants and wildlife of the area.
You can find it at the Mata Bookshop in Marbella's old town:
Libreria Mata
Enrique del Castillo 3
29600 Marbella
Telephone 952 770 144
If you visit the Marbella Tourist office there is ia book they give out about walking and trails, not only in Marbella, but in other parts of the Costa del Sol too. I don't know if they have issued this book in English, but I have a feeling they must of.

The book is called "Guia de senderismo de la Costa del Sol Occidental".
Marbella Town Hall. Tourism Office.
Glta. Fontanilla, S/N
29602 Marbella
Telephone 952 771 442