A few months ago, Susan and I bought the house adjacent to ours; it was up for short sale, and the price was too good to pass up. For various reasons, the house became an extension and expansion of our current residence (we briefly had other plans, but they didn't work out, so here we are!). We spent a couple of months doing some repairs and renovations, having bookshelves built, installing an upgraded security system, etc. Now that I've finished with that, I've been gradually setting up a library there, and in the process I've uncovered books that I forgot that we had, and discovered others that I remembered but haven't seen in years.
Revisiting the past through our books is fascinating; the oldest quality hardcovers date back to 1975, when Susan and I first began earning enough money that we could afford to buy real (that is, non-book-club) hardcover editions of some of our favorite authors' works.
I lost interest in most science fiction back in the 1980s, at which time I got rid of thousands of paperbacks and hardcovers--but it's interesting that I chose to keep most of the books that we purchased during the mid-70s, probably because I remember how carefully we had to budget, and how we had to make careful choices as to which books we could buy in hardcover and which would have to wait for paperback editions.
I also began investing in specialty books and hardcover limited editions at this time; I have more Donald M. Grant editions than I realized, as well as most Arkham House editions from those years. Each of those books carries a story beyond the one printed on the pages; each book is a tangible link to our lives at the time we bought it, and I can even remember carefully placing each volume on the bookshelves that I had built and finished in the summer of 1974. I had planned ahead, spacing some shelves for the larger hardcovers that I knew we would be able to purchase once I finally finished my student teaching and got a full-time job as an English teacher. (It's been more than a third of a century since I constructed those shelves, but I can still remember which shelves where reserved for non-fiction, which shelves were for art books, which were for SF, which were for fantasy, which were for mystery...)
Thus far, I've chosen not to move my 1974 bookcases to the other house; we're using them in the basement here instead. We do have substantial bookshelf space there, though, having added 9 bookshelf units, so I've been able to expand and reorganize a lot of books that had been clustered, stacked, or boxed since we sold the Horseleg Creek home back in 1999 and moved everything here.
There's not much furniture in the second house; there really doesn't need to be, since we're not living in it as such. We made some upgrades to the HVAC system and did a few other things to make sure that it is perfectly liveable should we ever choose to spend more time there, but for now, it's a very comfortable expansion of our current home, just a few steps away.