I think it was also the timing that the books came out, and that they were more or less travel blogs with card games and shoot outs. To quote a post on a forum

I think it was also the timing that the books came out, and that they were more or less travel blogs with card games and shoot outs. To quote a post on a forum where they read every james bond novel, there was this interesting tidbit: "[The books] serve as a looking glass into life in the 50s and 60s. The Bond series was a form of escapism for red-blooded British men still living under rationing until 1954. In a world where the average reader has probably never left smoggy England except for war service and is still living off of Spam and brown bread while puttering around in a used Morris, James Bond gets to travel to exotic locations from sea to shining sea, eating all the local cuisine that the audience may have never even heard of and driving rare sports cars in breakneck chases." I always thought that was an interesting take. It might explain why a set of books that were not widely regarded as the most well written, with multiple pages dedicated simply to how certain drinks or food in a certain region are made and taste, took off precisely for the same reasons that it might be classically regarded as "bad".