I know this well. It's a shame the wonderful, dry smell I associate with old books is just a sign that they're being eaten away.
Just for fun, a random sample
of my library. My Polybius from 1844 is a wonderful experience: good printing, fine cloth paper, a little foxing for character but not enough to make reading impossible, and of course the wonderful aroma. I have books printed less than 10 years ago that'll not survive another 10 at all, and this Polybius will still be useful and sturdy for another 100 years at least.
Your library looks a lot like mine, except my book shelves are scattered all over the house and I also have a lot of gardening books (in their own special book case) and tons of music books etc. The climate here must be kinder to books as I still own paperbacks I bought over 30 years ago and my old books are still in very good condition apart from the normal wear of using them. Some of the 2nd hand paperbacks are from the 1950's and still holding up well. I guess if we wanted to pay for books with sewn sections and properly bound they would last several hundred years, but each book would probably cost as much as a small TV set.
Paper was often a lot better, even during WW2, as I often play in a big band and the guy who runs it still has original charts from the 40's. A lot of them were quite small as paper was scarce, but despite nearly 60 years of being misused by musicians most are still OK, although we have photocopied a few sets which were getting fragile. Those old musos must have good eyesight, reading half sized charts in smokey nightclubs! On this subject, does anyone know why so many of the older books (Victorian era) used such small print?