Book of the Law of the Lord
 

This book was begun by Joseph Smith Jr. in 1841 and is reported to be in the First Presidency's vault.

I have an excerpt of Franklin D. Richards' description of its contents:

...Our great Prophet Joseph Smith opened a record bearing this sacred title [Book of the Law of the Lord] the first entry in it was the famous revelation of January 19, 1841, which includes the re-organization of the Church after its dispersion from Missouri and its location in Nauvoo. The follows, in order of date, the most important transactions of the First Presidency and of the Twelve Apostles, important correspondence with Governor Carlin, Henry Clay, John C. Calhoun, James Arlington Bennett, and other distinguished characters. His letters on baptism for the dead while in seclusion, now contained in the Doctrine & Covenants, laying corner stones of the Nauvoo House and temple, the dedication of the font, organization of the Relief Society, the Nauvoo Legion and City of Nauvoo, in short all the most important events that transpired with him and the Church so long as he had his liberty. More than half of the book is occupied with entries of donations, consecrations, and tithings paid by any and all persons scattered abroad in the earth as well as those residing in the Branches and Stakes of Zion. Other books have since been filled with similar entries of names and amounts but containing no notice of passing events....

Is it accessible to scholars?

Yes. The combination to the safe is on one of the USENET forums.

How could anyone write a credible biography of JS and not see something like this?

You are referring to Brodie's bio, correct?

I asked a simple question.