Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:
Explain the theme of this book.

### Input:
The Catcher in the Rye

### Response:
The theme of The Catcher in the Rye is of alienation and identity, captured through protagonist Holden Caulfield's cynical narration and his difficulty connecting with the world around him.