To get a detailed look into artbooks before buying i can´t recommend parka´s blog enough. He is that guy you allways find on amazon with his videos. His blog contains tons of artbooks with page fotos and videos. For example: Parka Blogs > Sketching - The basics
For sketches that leaves you speechless I would also recommend a little "must have" book: Cosmic Motors by Daniel Simon. This Book is full of scribbles, mid-level and detail sketches and also with fully modeled + rendered vehicles. I think after Tron & Captain America he is well known in the entertainment industry. He is an industrial-design professional who studied transportation design and worked for car companies before going into the film bussiness.
the book review: [Cosmic Motors - Daniel Simon](http://parkablogs.com/content/book-review-cosmic-motors)
p.s
another book is “Car Design Studies” It contains a lot of student works from the transportation design college in Pforzheim/Germany. The works are made in corporation with different car companies and are full with different car sketch styles. I have that book at home. When i have time I make some fotos.
Car Design Studies by Othmar Wickenheiser
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Berkey even better, though the prices of his books online are astronomical (much like the out of print Mead books).