My grandmother’s brother was a navigator on a B-17 and was killed during the war. He kept an excellent journal (he was planning to be a journalist after the war) and his wife compiled his journal entries along with her experiences into a vanity published book. There are only a few copies extant among family members, but I’m reading it now for the first time and it’s a fascinating resource with lots of interesting technical information. I’m wondering if there is some sort of archive somewhere that would be able to preserve the book for historical purposes.
As he was an American serviceman, the best place to get in touch with is probably the Veterans History Project at the Library of Congress. They would possibly be interested in material such as this to add to their collection and preserve (they take a lot of stuff and have fairly easy to meet requirements, but I don't want to speak in definitive without knowing the specifics of what you have). Check out their page here: https://www.loc.gov/vets, although they would be interested in the original journal rather than the published book, if you still have that. All the same though given their mission I'd suspect they are more interested in something like this than you would find with a museum. Plus of course, in my opinion at least, there is the added benefit that it is the Library of Congress so you are placing it in just about the most accessible place you could.
You can also find more information about them from the AMAs that the organization has held with us in the past:
https://www.reddit.com/r/AskHistorians/comments/3zevmy/ama_the_library_of_congress_veterans_history/
If you don't have the original, or wouldn't want to donate it, they provide a list of other places which might be interested in different criteria, although I would of course note that each one will have their own preferences as to what they are looking for, so many may be false leads.