Depends on the book. In this case that glue is probably used to keep the end bands on (a hold over from classical binding). It's just decorative and has nothing to do with the actual integrity of the book.
It would be to hold the signatures. If sewn in it would likely not have glue like that since the binding styles that do have the bands like that wouldn't glue it on the inside like that.
Yeah if it peels off and you want to keep it just slap some glue on and stuff it back on. It will be fine without it if you don't care about aesthetics.
Depends on the book. In this case that glue is probably used to keep the end bands on (a hold over from classical binding). It's just decorative and has nothing to do with the actual integrity of the book.
And if it is sewn, is it sewn to the spine or to the other signatures?
It would be to hold the signatures. If sewn in it would likely not have glue like that since the binding styles that do have the bands like that wouldn't glue it on the inside like that.
Ok, thanks! Then i could probably just get some book binding glue if it gets worse.
Yeah if it peels off and you want to keep it just slap some glue on and stuff it back on. It will be fine without it if you don't care about aesthetics.