Dr. Seuss The Lorax

My son has a good 10-15 Dr. Seuss books, but I've never heard of The Lorax.  I don't know if that's just me or if there are people out there that have not heard of it.  With the movie coming out this weekend, I decided to go out and buy The Lorax book for my son today so he can familiarize himself with it before I showed him a trailer of the movie....so he can decide for himself if he wants to go see the movie in the theater or not.  So for bedtime tonight that was one of the books that I read to him.  Along with The Lorax book, my son chose another Dr. Seuss book called Oh, the places You'll go.  Until tonight, I did not realize that not all of the Dr. Seuss books are kiddish but there is actually a point that Dr. Seuss is trying to get across to the children.  The message that he's trying to say is pretty deep I feel for a child to understand.  I do not know if my son really understood what the story The Lorax and
Oh, the places You'll go is all about.  I also don't know if by the time he could comprehend something that deep, that he would even want to read a Dr. Seuss book.