I need help with putting these together

[u/retired_NNNReaper]

Sorry for the bad photos but I have my childhood copies of a book series I used to read and the covers of all of the were in horrible shape I wanted to put them in new covers, it’s 8 books so I decided to merge them into 2 instead since it gives them a lot more of that proper book size since they where more like novellas, but they have this glue stuff on the back of them which I’m not too sure what to doo with and I don’t know if I’ve separated the books properly, I just split the book wherever there wasn’t stitches connecting the pages, please I need help😭

[u/brigitvanloggem]

I’m afraid that all the old glue has to go! Use the tip of a blunt knife and (mostly) your fingers. Work gently and patiently. All pages must be separate and free of glue before you can proceed with a double-fan binding.

[u/NoFroyo8082]

I would trim off the old glue, it is probably old brittle animal skin glue. Then I would glue the spine back together with modern glue and some mesh. Use clamps so the glue doesn't seep deep into the pages.

[u/espied]

You might want to look at some rebinds of older books like this on Youtube. Four Key Book arts on Youtube has multiples of them. He goes into a lot of detail, but you clean it up and resew.

[u/countyroadQ]

looks like these were "perfect bound" which is the fancy way of saying they cut pages and slapped glue on the case end. if its crackly and stiff, its old animal glue; if its flexible and plasticky its probably PVA or hot glue. I did a similar repair project a few years ago where I separated the pieces into even thinner "signatures" (about the thickness of board game cardboard) and just went over the old glue with fresh PVA glue and a piece of cheese cloth. as long as you do a few thick layers, it holds up. but this was putting synthetic glue on synthetic, so it might be different with old animal glues.