Which book of the Bible is completely godless (doesn't mention God)?
The Book of Esther
That's one of the reasons Martin Luther hated it so much.
Here's a quote about Esther from Martin Luther's "On the Jews and their lies":
Oh, how fond they are of
the book of Esther, which is so beautifully attuned to their bloodthirsty, vengeful, murderous
yearning and hope. The sun has never shone on a more bloodthirsty and vengeful people than
they are who imagine that they are God's people who have been commissioned and commanded
to murder and to slay the Gentiles. In fact, the most important thing that they expect of their
Messiah is that he will murder and kill the entire world with their sword. They treated us
Christians in this manner at the very beginning through out all the world. They would still like to
do this if they had the power, and often enough have made the attempt, for which they have got
their snouts boxed lustily.