Earth's Children hexalogy

1. 

   Book 1

   The Clan of the Cave Bear

   Jean M. Auel

2. 

   Book 3

   The Mammoth Hunters

   Jean M. Auel, J.M. Auel

3. 

   Book 4

   The Plains of Passage

   Jean M. Auel

4. 

   Book 5

   The Shelters of Stone

   Jean M. Auel

5. 

   Book 6

   The Land of Painted Caves

   Jean M. Auel

Book data and covers from Open Library (openlibrary.org).