<div><div>This book envisions the confines of medieval manuscripts as the potential territory of many virtual worlds: realms that readers call forth through their imaginative interactions with a book's material features. Each component of a medieval manuscript--its alphabetical characters, pages, images, text, gloss--offers an avenue of involvement with the world of books, and with the worlds <i>in</i> books. The explorations presented here follow those paths in a selection of manuscripts and texts produced in late-medieval Britain, tracing the fortunes of characters who become subject to and sometimes subjects in the very books the read and write. </div></div>