They’re finally out! McConkie wrote concerning the Lectures: “They were not themselves classed as revelations, but in them is to be found some of the best lesson material ever prepared on the Godhead; on the character, perfections, and attributes of God; on faith, miracles, and sacrifice. They can be studied with great profit by all gospel scholars.” They were prepared by Joseph Smith and Sidney Rigdon as lesson material for the School of the Prophets in Kirtland, and were included in editions of the Doctrine & Covenants from 1835 through 1921. A good overview of their significance is available in the Encyclopedia of Mormonism (also the source of the quote). The Lectures are well worth a read, and quite short.

Get the e-book free on PG. You can also scans of the 1835 edition at the Joseph Smith Papers site.