Book Broke in Two

G'morn, y'all. I went through the morning thread, VicNews & Commentary (thanks, Vic), and scanned the rest of the comments. I have plowed through the Book post and all its amazingly varied content as usual.

Probably my only bookish contribution today:

Despite my trying my best to handle it gently, my 1911 copy of Washington Irving's Sketch Book broke in two, right about smack in the middle. I'm concerned individual pages may be getting loose next.

What do you call the little bunches of pages, little booklets, that are combined for a hardback? I'm sure there's some printer's term I might've even known once decades ago. Anyway, looks like there's a paper that wraps around them, to which they're all bound or glued, and that's what's become torn, or rotted away, between two booklets. Only one thread still links the two sections. (I'm describing this poorly, I think - a pic would be worth 100 words.)

I have no idea if or how I could do a decent repair myself. Probably won't try getting a pro book re-binder to work on it. Hate this nice old book falling apart, though.

Now to peruse the bookthread comments. But first, a refill of the ol' coffee mug.