I find this interesting as well. I already have most of the room sidewalls covered with bookshelves, and contemplate to move two or three more from another room to the wall behind the listening position. This wall is now blank, part from one painting.
Perhaps this sort of room treatment works even better if you can live with arranging the books in a way that make the overall surface more irregular? Push in some books and pull others out a bit!
If bookshelves improve the in room sound it also has the benefit to call for more combined libraries and music rooms in peoples homes.
Fill the shelves with books - assorted sizes, and with varying spines - and don’t align all the spines. It will provide a measure of scattering, and I thing a little absorption - far better than a plain wall. And the room will look good too!
Yes indeed. I’ve not purchased Folio Society editions for some time now. I used to work in London several years ago and would always have a book to read during the Tube ride to work each way. Now I walk to work and I’m unable to multitask. I used to pick up bargains in the sales as the books are pricey. But they are wonderful editions, with an amazing array of titles. Worth every penny.