T. Kingfisher's The Hollow Places but make the monsters Sesame Street Muppets.

It deals a lot in nostalgia and the grief of leaving your childhood behind. Or, more like your childhood being stripped from you before you were ready to let it go.

The first chapter definitely left me terrified, and there were a couple of other moments early on that effectively scared me. However, the ending felt a bit rushed and didn't quite deliver on the fear from those initial chapters.

Still a fun read if you were maybe a fan of those jump scare, lore-heavy games like Five Nights at Freddy's, etc.