Gaster is very smart!... in science. Maybe not in other areas...

What is Undyne reading? I'm not sure! I mainly put it there for narrative mirroring. "Siqua worries about her parenting, Gaster tells her to just give them books, and she comes home to Undyne reading a book." Yikes! (In all probability, it's probably an illustrated novel or a how-to rock climbing book.)