It varies. Some of RL Stine's novels might have just a few main characters, while others could have a larger cast. But usually, you can expect around 5 to 10 significant characters.
The number of characters in an RL Stine novel can be quite diverse. It depends on the plot and the story's complexity. Sometimes, there might be only a handful of central characters, but in more elaborate tales, there could be up to 15 or so.
It's hard to give an exact number. RL Stine's novels don't have a fixed character count. They could have as few as 3 or 4 key characters or as many as a dozen or more, depending on the specific story and its requirements.