I had the same problem with some old books and after searching round the web found that absorbent cat litter seemed to be the cure recommended by several book dealers. As I had no cat litter I sealed some of the books in a plastic sack with an air freshener but this wasn’t very effective.
The books have been in a heap in my computer room for 3 or 4 months now and the central heating seems to have dried them out and got rid of the smell but it did take a long time.