It is a good yarn, Bags. She did a lot of research into what was known when she started on the saga (it was intended to be 12 books) and inferred more from anthropological accounts of surviving "ancient" cultures to fill in the gaps with how they might have been living. The descriptions of the flora and fauna are stunning, if anything too detailed - you get bogged down in the minutiae.
They are (more or less) about the progress of man from near-animal to inventor of tools and more sophisticated ways of living, and the conflicts between conservatism and innovation, with a human girl as heroine.
"Clan of the Cave Bear" is the first, and to my mind the best. The next, "The Valley of Horses" is also good. After that they get a bit samey, and I got the impression that she was running out of steam, but still had a stack of data to get through. I believe there are six finished. Whether she will manage twelve is another question.