I believe the OP was asking about taking photos to have published in a book. In this case he is intentionally flying and taking photos to be published in a book as a commercial venture, if the person publishing is doing it for any type of monetary gain. At this point it no longer falls under a hobbyist regulations and falls under commercial operation which would require Part 107.
Go back and read the OP again... the images were already taken previously as a hobbyist and LATER became valuable. The flights were completely HOBBY/RECREATIONAL and no rules/laws were broken. They LATER became valuable in that someone wants to now (NOT AT THE TIME OF THE FLIGHT) use them in a book.
Now IF the OP decides to take additional pictures with the intention of "possibly" using them in this book it's outside of Hobby/Recreational and as such has pierced the protective bubble and defaulting THOSE flights (not previous flights) to Part 107.