It doesn't look like much, but then, it wasn't supposed to. This unassuming book is a quarto edition of Thomas Middleton's The Spanish Gipsie (London: Printed by I.G. for Richard Marriot, 1653). In the 16th and 17th centuries, most plays were seen by printers as ephemeral materials, and they issued them as inexpensive quartos, loosely stitched together with flimsy paper covers. If a reader of a play decided to keep the cheap publication, he or she would usually bind it together in an assemblage of plays collected over a period of time. In the 19th century, collectors broke up these assemblages and had them individually bound--often in very expensive bindings expressing the new importance society placed on these publications.
This first printing of one of Middleton's plays somehow managed to escape being stripped of its original paper wrapper and survived to the present day with cover intact. It is now a perfect example of the way plays by Rowley, Middleton, and Shakespeare appeared to their first readers.
You can see this extraordinary survival by asking for Rare PR2714.S7 1653.