This is the list of the current number of books in the Mosly Ghostly series. The books were all written by R.L. Stine.
Mostly Ghostly #1 "Who Let The Ghosts Out?
Mostly Ghostly #2 "Have You Met My Ghoulfriend?"
Mostly Ghostly #3 "One Night In Doom House"
Mostly Ghostly #4 "Little Camp Of Horrors"
Mostly Ghostly #4 "Ghouls Gone Wild"