This is a book version of a 1952 Disney short directed by Jack Hannah (not the same Hannah as Hanna-Barbera) and written by Bill Peet, who went on to write dozens of children’s books (all of which are still in print) including Kermit the Hermit (1965) and The Ant and the Elephant (1972).
Lambert is loosely based on the Grimm’s fairy tale, “The Wolf and the Seven Young Kids” and tells the story of a lion raised by sheep, who feels different all his life, until one day he has a chance to be a hero.
The theme is similar to Rudolph the Red-nosed Reindeer, where a trait that makes the main character feel excluded turns out to be valuable. But this story has a bit more appeal to my kids, who see Rudolph as a bit of a wimp, while Lambert is obviously powerful and only needs to tap into his latent ability.
I sometimes hesitate with books from the 1950s since they are often more violent than I would like, but this one is pretty tame, other than some head-butting.