Your question was:
> What is the book of jasher that is spoken of in 2Samuel1:18?

"Jasher" means "upright,", so literally, the Book of Jasher means the "book
of the upright."  It was evidently a kind of national song book of the
Hebrews (cf. Joshua 10:13).  Here is an exerpt from The Online Bible about

"Upright. "The Book of Jasher," rendered in the LXX. "the Book of the
Upright One," by the Vulgate "the Book of Just Ones," was probably a kind of
national sacred song-book, a collection of songs in praise of the heroes of
Israel, a "book of golden deeds," a national anthology. We have only two
specimens from the book,
 1. the words of Joshua which he spake to the Lord at the crisis of the
battle of Beth-horon #Jos 10:12,13
 2. "the Song of the Bow," that beautiful and touching mournful elegy which
David composed on the occasion of the death of Saul and Jonathan #2Sa

There is no copy of this book which exists today.  Some have referred to the
Book of Jasher as one of the lost books of the Bible.  This is misleading,
since it suggests that part of God's word in missing.  However, divine
inspiration is never attributed to the Book of Jasher.

I hope this helps.  Thanks again for your post, and God bless.

Joe Price

Joe R Price

Bible Answers

Mt. Baker church of Christ