He is most famous for his "Little" series, which features a simple bunny as the protagonist in various scenarios. Some of the most popular books in the series include:
* Little Blue Truck
* Little Yellow Digger
* Little White Rabbit
* Little Red Hen
* Little Cloud
Bruna has also authored and illustrated many other children's books, some of which include:
* The Story of Babar (reillustrated)
* The Elephant
* The Cat
* The Dog
He is known for his minimalist style, using bright primary colors and simple shapes to tell heartwarming stories. His work has been translated into over 50 languages and is beloved by children all over the world.
If you are referring to a different F.J. Bruna, please provide more context or information.