Some of the central themes or morals of "Holes" by author Louis Sachar include fate and determinism, friendship and its advantages, the importance of history in everyday life and cruelty. According to the author, it was never his intention to write a grim or frightening story; however, many readers have found it to be so.
Of the moralistic themes, the mutually beneficial nature of friendship is among the most apparent. The bond between Stanley, the protagonist, and Zero ultimately leads to both of their survivals, not to mention their getting rich.
Explorations of the destructive effects of cruelty, which are also the parts of the story that many readers have found to be grim, include Mr. Sir's arbitrary punishment of Stanley for his own mistreatment at the hands of the warden.