It’s fine.  I suppose it’s a good idea for all library collections to include a story about the kid who doesn’t want to have a babysitter, and this would work, but I’m not sure you can’t find better out there.  It’s a pretty basic story:  Tiny Troll is watching his mother get ready to go out for the evening, protesting that he doesn’t want a sitter, kindly older sitter comes, Mom goes, Tiny Troll throws tantrum, calm and nurturing sitter wins him over with mudmilk (monster equivalent to cocoa?) and a story, Tiny Troll falls asleep, and Mom returns safely.   The only thing that makes it particularly unique is the monster twist.