Book for Heritage Speaker?

Looking for a book to gift to a friend who is a heritage speaker of Japanese but doesn’t have much experience reading Japanese. He’s trying to read more so he can improve his reading speed and recognition of written words in Japanese. He’s currently reading Kafka on the Shore, so I’m looking for a recommendation of a book on that same level (approximately) for him to read. Maybe not another Murakami book so he can branch out and be exposed to other authors, but I’m open to any recommendation at this point.