Folio - a book (or manuscript) consisting of large sheets of paper folded in the middle to produce two leaves or four webpages; "the very first folio of Shakespeare's performs" Private or particular libraries produced up of non-fiction and fiction books, (in contrast to the condition or institutional data kept https://davidhoffmeister.com/david-hoffmeister-the-message/metaphysics-of-a-course-in-miracles/