Among his best-known works is The Coldest Place on Earth (Oxford Bookworms, Stage 1), a gripping account of the early twentieth-century race to the South Pole. He also wrote The Year of Sharing (Stage 2), a thought-provoking science fiction tale about a boy sent to live in a community where humans coexist with animals. Another notable title is The Star Zoo (Stage 2), which imagines a future Earth where all animals have disappeared and follows a young girl who discovers a spaceship filled with living creatures.
Gilbert's writing is praised for combining clear, controlled language with genuine storytelling power, addressing themes such as nature, technology, and human responsibility. Through his works, generations of English learners have experienced the pleasure of reading engaging stories while developing their language skills, making him a respected figure in the field of graded readers.