Good call not using heat on that glue. I had a paperback start to split and tried a hair dryer once. It made the glue brittle and a whole chunk of pages came loose. What worked for me was a thin layer of PVA glue applied with a toothpick along the spine. I clamped it shut with some heavy books for a full day. The repair held up for years after that.
Ever try fixing a book with tape? I used some clear packing tape on a split cookbook spine once, and it made the pages stick together in a weird clump. Charlesk88's glue method sounds way smarter for keeping things flexible.
Yeah tape is a total mess for book repair. It gets gummy and ruins the paper over time. What I do now is use a small paintbrush to spread white glue along the spine, then press it flat under a stack of textbooks overnight. The key is using a weight instead of clamps so the spine stays straight. My old paperback dictionary is still holding up after a fix like that.
That sounds like a total nightmare waiting to happen lol. Heat can really mess up that old glue and make things worse. Glad you trusted your gut on that one.