I read TLP first as an adult* and quite enjoyed it. I also happen to own a copy in Latin, but that's kind of more because it's still a novelty to find "modern" books translated into Latin. And I used to have a usericon (not on this forum) of one of the illustrations with "
Ceci n'est pas un chapeau", so admittedly I'm kind of biased.
I'd say give it a try. It's short and pretty nifty and doesn't talk down to the reader the way some books written with children in mind do. I consider it to be an "all-ages" read in the truest sense of the word, where there's bits aimed at children and bits aimed at adults and everyone can get some enjoyment and understanding from it.
* The actual version of TLP I read as a child was a parody in the satirical
The Book of Sequels, called
The Big Fat Balding Prince, and in retrospect, it's even funnier.