Over the past thirty years, one of the biggest-selling historical series around has been the Earth's Children sequence by Jean M. Auel. With sales of 45 million for the five existing books, it is one of the most popular series of books of recent times (slightly outselling Robert Jordan's Wheel of Time sequence in total numbers and radically outselling it in terms of sales per book, for example), although also one of the longest-gestating. The publishers have confirmed that Auel has handed in the manuscript of the final novel and are planning an ambitious multi-territory launch (which so far stands at eleven countries).
The books are set approximately 30,000 years in the prehistoric past of Europe, and chronicle the rise to supremacy of Cro-Magnon humanity over the fading Neanderthals. The previous books in the series were The Clan of the Cave Bear (1980), The Valley of Horses (1982), The Mammoth Hunters (1985), The Plains of Passage (1990) and The Shelters of Stone (2002). The final book will be entitled The Land of Painted Caves and will be released on 29 March 2011.
I haven't read any of the books, but according to reports they centre on a young woman who is raised by Neanderthals, is exiled and spends enormous amounts of time having sex, as you probably would in caveman times if you were feeling pretty bored. Reviews of them appear to be somewhat mixed, to say the least, but this will certainly be a high-profile release next year.