An extremely brief description would be that it is the story of an archeological dig that takes you to the beginning of a time and brings you back greatly enriched.
I actually read this book many years ago. And of the hundreds of books I've read since, it still remains my favorite. If you do not enjoy detail in a story, this book is not for you. It is very long and worth every minute. There is no real way for me to give a true synopsis as it is just too overwhelming for me to try to shrink it down to a few words. I think it would be an injustice to do so.
If you love a story that takes you with it, don't pass this up just because the book is thick. Sometimes great things come in big packages, too.