It tells the story of Lumpawarump (Lumpy), Chewbacca's son on Kashyyyyyyyyyyyyyyyyyyyyyyyyyyyk. (OK, there are only 3 y's) There are a bunch of neat little bonuses. We get a glimpse of the swamps of Kashyyyk, beneath the Wookiee's treehouses. We learn that the Wookiees were once enslaved, but that Han Solo triggered their revolt and emancipation. This is how he met Chewie. We also learn that adult Wookiees have telepathy that can reac hacross great distances. Chewie also flies a little red-striped 2-seater explorer ship out of the Millenium Falcon, down into the swamps of Kashyyyk. Wouldn't that have been better for saving Luke on the Bespin weathervane?
Published by Random House, illustrated by Patricia J Wynne, no author is listed. It's out of print, but not impossible to track down. Get it and read it to your little ones.