Excerpts from Talmud Bavli
Rosh Hashanah, Ch. 16, V. 3
R. Kruspedai said in the name of R. Johanan: Three books are opened [in heaven] on New Year, one for the thoroughly wicked, one for the thoroughly righteous, and one for the intermediate. The thoroughly righteous are forthwith inscribed definitively in the book of life; the thoroughly wicked are forthwith inscribed definitively in the book of death; the doom of the intermediate is suspended from New Year till the Day of Atonement; if they deserve well, they are inscribed in the book of life; if they do not deserve well, they are inscribed in the book of death.
According to tradition, the first man was created on Rosh Hashana. The Midrash says:
When the Holy One, blessed be He, created the first man, he took him and returned him to all the trees of the Garden of Eden and said to him: See all that I have created, how beautiful and praiseworthy. Make sure that you do not spoil and destroy my world, because if you spoil it, there is no one to fix it after you.