The Cave Painters by Gregory Curtis (2006) is the most accessible account of the discovery and interpretation of Ice Age cave art, from Altamira to Chauvet. Curtis writes as a journalist rather than an archaeologist, which makes the book engaging without being dumbed down. Essential reading before a visit to Font-de-Gaume.
The Mind in the Cave by David Lewis-Williams (2002) proposes a controversial but compelling theory about why Paleolithic people made cave art — connecting the imagery to shamanic altered states and the neurological phenomenon of entoptic patterns. You may not be convinced, but the book will make you look at the paintings differently.
The Dordogne by James Bentley is an older but reliable regional guide that covers the Vézère valley's history and landscape alongside the prehistoric sites. It reads more slowly than modern travel writing but contains a lot of information not easily found elsewhere.