The Wild Robot
This middle-grade science fiction series follows a robot who washes ashore on a wild island with no memory of how she got there and must learn to survive in a natural world she was not built for — and in doing so, raises a gosling she accidentally orphaned and becomes part of the island community. The series is quietly beautiful and emotionally affecting, dealing with themes of belonging, the relationship between technology and nature, and the love between parent and child.
Percy Jackson and the Olympians
This five-book middle-grade fantasy series is set in a modern America where the ancient Greek gods are still very much alive and active, and follows a twelve-year-old boy who discovers he is the son of one of the Olympians and is drawn into a conflict between gods that threatens to start a world war. The series is fast-paced, funny, and packed with Greek mythology adapted for contemporary readers, and launched one of the most successful franchises in modern children's publishing.