I got to see the 2nd Edition of Hucho from the MIT library, via my wife who is a librarian at Harvard. I now own the 4th edition that I bought from Amazon. Here's the Amazon UK page for it:
Aerodynamics of Road Vehicles: Amazon.co.uk: Wolf-Heinrich Hucho: Books
If you can find the 2nd edition (used?) then buy it. I think it had several very useful things that seem to be edited out of the 4th edition; including several pages on air flow inside the wheel well with a spinning wheel. But, I think only the 4th is available new - and it is certainly well worth buying, in my opinion.