The Book of Life

I was in a Bible study yesterday. They were referring to the book of life, and I did know what they were referring to. Can you help me out with that? Yeah, there are only a few references to thebook of life in the Bible. There's actually this 32 where Moses is praying to God because judgment's coming on Israel. And then Revelation, the 20th chapter, says that all those whose names were not written in the book oflife were cast into the lake of fire.