I've lost several shelves of books when we moved to a different country. Before ebooks became more commonplace, I've re-purchased some old favorites and have bought new paper books.
Right now, I've re-purchased part of my collection in ebook format whenever available and the rest are slowly going to 1DollarScan to be converted. Our apartment's just too tiny to house my book collection (have books in the closet, underneath the bed, underneath the sofa, etc). I still plan on keeping dead tree versions of absolute favorites but all of those, I should be able to fit in two tall bookcases.
