This is an old favorite of mine (I first read it in high school) that I finally got a chance to finish re-reading. It's the first and best book of the Earth's Children series, a series of books about people in prehistoric Europe. There is great attention to detail, though not always quite accurate (scientific understanding has changed a bit since it was researched and written in the late 1970's and published in 1980).
"Oh, you can’t help that," said the Cat: "we’re all mad here. I’m mad. You’re mad." "How do you know I’m mad?" said Alice. "You must be," said the Cat, "or you wouldn’t have come here.”
