Actually, Lewis Carrol was on an outing with his family, which included his niece, Alice, who seemed bored. In an attempt to entertain her, he told her stories based off his drug experiences, and worked her name into the stories to keep her interested. Alice's Adventures in Wonderland is actually a compilation of short stories Carrol would tell Alice at various times. When he later published the book, he threw all the short stories into a series of two books, which also included Through the Looking Glass: More Adventures in Wonderland.
And I can't wait for this movie, for Manson's interpretation either. The Wonderland series is my favorite collection of stories I've ever read. stoked!