"Glued" versus sewn bindings.
One important factor in rebinding is knowing if you have a sewn binding. The popular term is "glued" versus sewn binding. However, most, if not all, modern Bible bindings are glued. Even if it is a sewn binding, it is still glued too. That is why I use "glue-only" for those that are not sewn.
A sewn binding is made when paper is folded over to form the pages. These sets of pages are called "signatures" (see above photo, upper and lower left) The signatures are sewn through the folds (see above photo, right), then to each other to form the book block. A mull cloth is then glued to the spine (shown in the above photo, lower left).
The danger of the glue-only binding is that that the glue will crack parallel to the spine. This allows the pages to separate. See photo below for examples. The Bible shown will soon be a pile of separate pages. The edges will get damaged, pages can get lost and the Bible will become unusable.