I’ve had a chance to experiment with a few different types of glues for my books and the best one I have come across are PVA glues which can be found in any art supply or craft store.
PVA is easy to work with and strong. This is just a common white glue that is very flexible and can be easily brushed onto the spine of the book. PVA glues are acid free and used in libraries to repair books. The biggest problem is slow drying time. You will need to keep the pages clamped together for a while as it dries. Adding another layer of glue to the book block later and attaching the cover works fine.
