The spine on my bible was really needing some repair before it became a big problem.
It was really starting to crack and pieces had come off already.
I was at Dollar Tree today and found this!
Pretty Duct Tape
I put one strip down the center with enough to tuck the ends inside the spine. Then one piece on each side.
You can see where I tucked it inside the spine and on the outside pieces I clipped the tape where part was tucked inside and part was just laid down inside the cover.
I have an embroidered cover I made many years ago so normally the tape will not show. But for now while the cover is off because it needs to be cleaned, this is bright & cheerful as well as functional.
You could use this method for pretty much any hardback book spine. If you have a valuable book I would suggest letting an expert repair it.