On the Book of the Wars of the Lord

What is the Book of the Wars of the Lord? We find it mentioned toward the end of Parshas Chukas, along with an excerpt, but what was it? What happened to it? And why did God to choose to quote from it as part of his divine dictation to Moshe?

Answers

1 - What was it? One of several non-canonical bible book, generally judged to be a lost work. Some scholars believe it was a work of military history; others say it was a collection of poetry and verse.

2 - What happened to it? It was lost. This is why it's judged to be a "lost work", see? I'm not aware of a reliable theory that explains why it was lost, though Robert Alter speculates that the book was not preserved because was too mythological. Later authorities, he says, were uncomfortable with a book that represented God as a warrior, in direct combat with Israel's enemies, rather than working through the agency of Israel. I'm not entirely sure why Alter feels comfortable with such a speculation given that just a tiny snippet from the book is extant, but there it is.

3- Why did God to choose to quote from it as part of his divine dictation to Moshe? This is a puzzle. Here's the exact quote from Num 21:

[Some stuff about camping and traveling and more camping and traveling]Therefore is it said in the Book of the Wars of the Lord "Against Waheb in a whirwind and the wadis of Arnon, and the cascades of the wadis that turns down toward Ar's dwelling and clings to Moab's border."

Cryptic no? If there was something God needed to say here, why didn't he put it in His own words? Why did He instead take something so muddled from someone else's book?