Nicholas A. Basbanes (1995): A Gentle Madness: Bibliophiles, Bibliomanes, and the Eternal Passion for Books.
This is the book to pick up if you feel guilty about having too many books: Basbanes tells of book collectors and their passion, describing the need to have many books and to keep them (and, occasionally, read them) as a psychological condition its sufferers have no need or desire to be cured of.
Basbanes writes beautifully, with passion and compassion, anecdote after story after chronicle of collectors from Winston Churchill to a man who stole more than 30,000 rare books from libraries around the USA. He dives into the rare book markets and their mechanisms and describes what collectors do to make sure that their collection lives after them (donates them to universities, mostly, with stipulations on where and how the books are to be kept.)
If you ever have felt guilty (as I have) about those cases of books in the basement and the lack of visible wall surfaces in your home, this is the cure: Basbanes make it all seem so normal, almost desirable.
How fitting that it is out of print – if you can get your hands on a copy, add it to you collection!