It's impossible for me to choose just one favorite book, but here are two that I really like.

The first is We Are Okay by Nina LaCour. This is a story about a young university student named Marin. Her grandfather died, and even though Marin's friends and girlfriend want to support her, Marin refuses to contact them or accept help. As the story continues, we learn why this is and what happened before Marin's grandfather died.

The story takes place during the winter and has a strong sense of atmosphere, so I usually feel like reading this story on cold days. It is also very moving and has a strong sense of love between the characters, which is comforting.

Another book I really like is Where the Wild Ladies Are （おばちゃんたちのいるところ）by Aoko Matsuda (and translated by Polly Barton). This is a collection of short stories based on Japanese ghost stories and folklore. I'm interested in folklore and mythology, and this book helped me to learn more about classic Japanese stories. The stories in this book are also interesting because they take place in the modern world and are mostly told from the perspective of female characters.

So far, I have only read this book in English, but the language is very easy to understand, so I think I want to try reading it in Japanese also.

If you are interested in ghost stories or stories about love, I recommend both of these books!