Babies like to put books into their mouths (along with everything else). It’s normal. It’s one of the ways they have of exploring the world. Here are a few hacks to deal with it:
Put something else in their mouth (pacifier, food, wet wash cloth)
Wipe hand sanitizer on the book and quickly wipe it off.
Use your hand to direct their hand to turn pages.
Take a deep breath, and just go ahead and let them do it.