The Plains of Passage is the weakest of the first four Earth's Children books. The first third of the book consists of sex, review, more sex, eco-lecture, still more sex. Please don't misunderstand: I am all about whatever moves the story along but there is no plot to the first half of the book and the only real action is between the furs. Ms. Auel has set Ayla as the archetype of the creative, inventive, progressive Cro-Magnon, but she has made Jondalar a caricature of the sex-obsessed, self-absorbed, take-charge-when-he-hasn't-a-clue macho caveman. It's a good thing she gave him a horse because after all of that, I doubt he could walk.Even in the second half, the narrative drags along. The frequent five-page geological history lessons begin to pall quickly and the constant rehash of the previous books reads like filler material. If you've read the series up to this point by all means check this one out from your local library and skip the first half.