Publishers feared what this might end up doing to their business, but what it might have done, at least in some cases, was launch books that weren't doing so well. In the case of The Great Gatsby, for instance, only 25,000 copies of the book had been printed between 1925 and 1942, but 155,000 copies of the Armed Services Editions were printed. Soldiers read them, recommended them to friends and families, so maybe (?) that instigated the Fitzgerald revival in the 1940's. It certainly couldn't have hurt.
At any rate, there's a new book out (referenced in the article I read), titled When Books Went to War: The Stories That Helped Us Win World War II by Molly Guptill Manning that examines the topic further.
I was so fascinated that I went online and found a copy (the books were originally planned to last about 6 readings, but there are many still available at bookstores or other sites that carry used or vintage books). Here's my new old copy of Mrs. Parkington (purchased on Etsy).
If you're interested in reading more, here's the article I spoke of (from the Wall Street Journal) as well as another article from history.net..