Destroy the book
A bit of a frame challenge here, but don't rebind or fix the book. Just destroy it.
Cut out all the pages, take the ones you want to conceal. And the cover/spine. Replace the pages (making sure to rough up the edges). Maybe add some additional artful distressing to both the real and fakes pages, to make the replacement harder to spot. Or even replace smore of the original pages (the ones you intended to leave) with exact duplicates, to help the fakes fit.
You could also take some of the unimportant maps, to make it look like that is why the book was damaged.
Then stuff them in a folder, or tie them up with twine. Or slip them all back into cover, if you don't want to take it, or the cover is important (and then you could still tie it with twine).
The real key here is making sure the PCs don't have any magic that can detect the forgery or reason for the damage (i.e. psychometry). Fortunately, those are fewer and far between in 5E.