I got Princess Mononoke as gift, when a friend heard that i have watch only the latest two movies of Hayao Miyazaki ( Howl's Moving Castle and Spirited Away).
In case you are not familiar with Miyazaki's work, you need to know that he was a different style of thinking and showing things. Most of his movies, have weird creatures, spirits, monsters and sometime you even need time to make sense of the movies. His work is different but definitely good. Of course it always depends on much you are into anime movies and ideas. Do not expect a Disney story (funny though, that the dubbed version of the movie are from Disney if i'm not mistaken).
Princess Mononoke became instantly my favorite piece of his work. I like the story way better, with the nature and the humans who don't respect it and instead of learning to live together, they destroy it and cause war. It's a movie of nature vs humans with main protagonists, a human boy and a human girl who grow up in the forest with the wolves. So together they try to show them, that even though they are really different and have different ideas they can still work together.
Princess Mononoke is for both kids and adults. It's not a fairy tale but something deeper with messages and i believe everyone can enjoy it. I would also recommend to watch the original version with the Asian voices. They are way more expressive than the dubbed version.