The Secret Book of Gnomes was a series of books designed for children. They contained stories and a guide to how Gnome

Gnome

A gnome is a diminutive spirit in Renaissance magic and alchemy, first introduced by Paracelsus and later adopted by more recent authors including those of modern fantasy literature...

s lived in harmony with their environment, such as what a Gnome has in their first aid kit and how a Gnome's house is built. They were written by the Dutch author Wil Huygen

Wil Huygen

Wil Huygen , was a Dutch book author. He is best known for the picture books on gnomes, illustrated by Rien Poortvliet....

 and illustrator Rien Poortvliet

Rien Poortvliet

Rien Poortvliet was a Dutch draughtsman and painter.Born in Schiedam, he was best known for his of animals and for "Gnomes" in the famous series of books by Wil Huygen and published by Harry N. Abrams, Inc. of New York City.Being a plasterer's son from Schiedam, making a living as an artist did...

, though they claimed that it was written by a Gnome called David. Those authors also created another series about Gnomes entitled The Gnomes.
That later was used as a basis for the television shows David the Gnome and Wisdom of the Gnomes

Wisdom of the Gnomes

Wisdom of the Gnomes is an animated series produced by Spanish company BRB Internacional about Gnomes. It was a spin-off of the series The World of David the Gnome...

 by BRB Internacional

BRB Internacional

BRB Internacional is a Spanish animation studio which is best known for producing 1980s cartoon hits such as Around the World with Willy Fog, Dogtanian and the Three Muskehounds and The World of David the Gnome....

.