- Encyclopedias and other reference works. These types of editions are by their very nature are prone being published in multiple volumes.
- Do you have a favorite author? There is a very good chance that you can find a collection of his or her works. From C.S. Lewis to Conan Doyle - take your pick.
- Collections of classical books. One such collection (Classical in more than one sense) is the Loeb Classics Library. This very prominent collection features almost the entire extant corpus of literary works from Greek and Roman antiquity (Greek and Latin texts with facing translations). There are many people who do not own the entire collection (about 500 volumes, I believe), but even if you decide to limit yourself to a specific subset of Loeb you will end up with a few very nice looking bookshelves that can be used for reference: ancient epics, ancient poetry, philosphical works etc. Just do not mix this collection with Harvard Classics. The Five-foot Shelf of Books. 52 Volume Set, which is an equally impressive set of books from later times.
- One of the most expansive book sets one can easily find for sale today is The Penguin Classics Library Complete Collection: More than 1000 of the Greatest Classics Keep in mind, though, that if your favorite authors are featured in this collection you can limit yourself to just their works. Of course, in case of Dickens or Tolstoy that means dozens and dozens of books!
- If are interested in theology there are many reference works and Bible commentaries that can be usually purchased at a very low cost.
Book clubs - a great way to build a home library