[Huz-Z]

I bought the book last year from a seller on eBay who had a number of them on hand.

Anyway, despite the fact that it pertains to the initial design of the Z4 and doesn't talk about the 2006 and later cars (the 3.0si, the new coupe or the M cars) it is still a great read for any Z4 owner. There's just tons of good stuff in this book with a great many color photos and diagrams. Just a quick flip through will demonstrate that it is very comprehensive and well put together.