What kind of book is a Turtleback ?

While I was looking for books for my daughter I came across this.

http://www.turtleback.com/faq.htm

A paperback with some form of cardboard stock affixed to the endpapers to make it more durable, like a sort of semi-hardbound edition. Also this term is used when the covers have been removed and pasted, sometimes under laminate, to a much sturdier binding. These are often found in libraries, especially in school libraries on popular fiction most commonly (and cheaply) found in softcover editions. Hence 'turtleback', because a shell has been placed over the otherwise soft & relatively squishy innards of a paperback.

Often used by libraries for titles that require additional stability, this binding is a paperback thht is reinforced (often with cardboard, sometimes laminated.)  Turtleback books are sturdy editions that are priced about the same as paperback books.

Thank you !