Had an opportunity to provide an office/library for a client (doctor-surgeon) a few years ago. He needed a work table, relaxing area, catalog research area, plus a place to keep his gazillion books.
We put the work table at one end of the room and the relaxing overstuffed chairs at the other end separated by an island for research catalogs. The island was used for laying books, research manuals, etc. on.
We raised the ceiling to 12' and extended the shelves up to maximize shelf space on TWO sides only and provided the classic rolling ladder. We also provided a narrow window, making sure the direct sunlight could not hit the books.
We proposed laying some special books on the floor in recess space and covering them with glass in two locations, but he nixed the idea...darn.
We provided a place for pictures and some special lighting to accent the two "walls of books".
I think the variety of spaces within the room helped. I'd encourage you to provide a variety of spaces, including a tv screen and computer space.
If these books are for show, I wouldn't put them in a room (library). I'd spread them out throughout the house: entry, halls, bedrooms, etc. However, I'd keep them away from moisture like kitchen, baths, mud rooms, etc. Glass doors is a good way to protect the rare books. (There is special UV glass to protect rare books and special HVAC systems too.)