The Mammoth Hunters by Jean Auel

In this book Ayla and Jondalar stay with the Mammoth people for a while during their travels back to Jondalar's family. We see Jondalar's jealousy and Ayla's inability to understand human culture (temporarily) confound their romance. I think the book gets too hung up (as others in the series have) on how early humans thought and learned and knew--more like a textbook than a story. The best part of the story was Rydag, the child of a human and a Neanderthal.