largest book stores/auto thematics (Frankfurt)

Dear Expat Friends and Locals,

Please advise where in Frankfurt I can find big book stores, which are likely to have a lot of books, magazines dedicated to cars? Actually, I am looking for this specific book by Lindsay Porter "How to Convert Volkswagen Bus or Van to Camper". I know I can order it online, but it will take too long, so I am ready to first try my luck with finding this book somewhere in Frankfurt, so that my father could have his Christmas present on time.

Thank you all very much for your help!

Best,
Yaroslava