We used this stuff called “Scott’s Liquid Gold Mold Control 500” it’s scary stuff. But works amazingly well—we weren’t using it on books, but on particle-board (Ikea) furniture that had been in storage.
It won’t undo any actual damage, but it will completely kill and remove any mold on both porous and non-porous surfaces. It may also lift the inks and/or eat the paper, but it might work. I would treat one page at a time, outside, and build some sort of rig to hold it while it dries.