Numbers 21:14 (NKJV)
14 Therefore it is said in the Book of the Wars of the LORD: “Waheb in Suphah, The brooks of the Arnon,
Could the book of wars be the one Moses wrote & recited to Joshua (Exodus 17:14-16)?
This book quoted above seems a little bit mysterious
What is the book of wars
Who wrote this book?
The same passage in the Septuagint reads, "14 On account of this it says in the scroll war (i.e. war scroll) of the LORD, Zoob set ablaze, and the rushing streams of Arnon. 15 And the rushing streams he established to settle Ar, and it lies near the boundaries of Moab." - TABP
In context, the fragmentary passage references another scroll to provide support for defining this boundary of Moab and Amorite lands. As previously pointed out, the identity of that scroll is speculative. The use of the tetragrammaton of the burning bush tradition provides evidence that this was an contemporary Israelite scroll known to Moses that might have contained a poem, song, or historical record, but not written by a prophet.
Dieter
I'll try to add sources as time permits.
This book is not mentioned explicitly anywhere else in the Bible, and there are a number of theories found in the commentaries.
Rashi, Rashbam, Leclerc, and Luzzatto (and presumably many others, all to Numbers 21:14) support the theory that this was not an actual book that was written, but rather it simply refers to this fragment of the Bible narrative.
Among more modern authorities, N. H. Tur Sinai claims here that it never existed.
Ibn Ezra to Exodus 17:14 claims that this could have been the book that Moses wrote for Joshua at the battle with Amalek. However, in Numbers 21:14, he suggests that it may have been written in the times of Abraham. Similar claims are found in various other commentaries.
(Wikipedia quotes David Rosenberg in dating the book to ~1100BC, and Joseph Barber Lightfoot that it is another name for the Biblical Book of Jasher. However, no sources are provided for either claim.)
NZY Berlin suggests that it was a book chronicling the battles fought and happening as the Israelites traveled towards Canaan.
Nahmanides, Abarbanel and Mendelssohn (see Luzatto for a rebuttal) seem to understand that these were books written by other nations at that time about known wars, and that it was not Jewish in nature.
Some understand that it contains mainly events that took place, whereas others seem to understand that it was a book of songs and poetry.
Side note: In this CBQ article by Duane Christensen, he attempts to reconstruct the text that we have in order to make any sense out of it, but notes that some have dismissed it as "beyond reconstruction".
