This book is a well-written and indispensable resource to enrich and supplement your study of the book of Doctrine and Covenants of the Church of Jesus Christ of Latter-day Saints. With a few exceptions, each revelation has its own chapter and each chapter is divided into three sections:
1) Origin. This section explains the origin and historical context of the revelation. This includes what is known about the person who the revelation is addressed to, what questions they are asking, what situation and circumstances they are in at the time they receive the revelation, etc. It often goes into considerably more detail than what is contained in the section headings within the text. This information makes it much easier to understand many of the revelations contained in the Doctrine and Covenants.
2) Content. This is basically a high-level condensed summary of what the revelation says, usually with considerably more detail than the chapter headings contained at the start of each section. It is also really helpful because whenever a revelation refers to or is related to the content of a previous revelation the author draws attention to that so you can more easily see/understand how various revelations are connected to one another. These summaries are also really helpful as far as giving a clear condensed summary of the doctrine being revealed or the commandments the Lord is giving. This really helped me better understand some doctrinal concepts much more clearly than I did before.
3) Outcomes. This section explained what happened or what changed as a result of the revelation. For example, when revelations are addressed to an individual it will explain whether that individual obeyed the revelation or not, and what the consequence was. When a revelation promises certain blessings for doing a certain thing and the person does that thing it will show what historical evidence there is of the fulfillment of the Lord's promised blessings for their obedience. It also illustrates in some instances the consequences of certain commandments being neglected or disobeyed. For revelations in which new doctrine is revealed it will explain how the revelation of that doctrine affected Joseph Smith, the trajectory of the Church, etc.
This book is truly excellent. It is really helpful from both a church history and a doctrinal learning standpoint. I understand the Doctrine & Covenants far better after reading this book than I did before. It especially helped me better understand the doctrine of agency, consecration, the temple, and exaltation. It also really helped me better understand both how God deals with his children and accomplishes his work while also respecting their agency.
FYI, this book is NOT a verse-by-verse doctrinal commentary of the Doctrine & Covenants. If you are looking for that I recommend the church's institute manual and the book Revelations of the Restoration: A Commentary on the Doctrine and Covenants and Other Modern Revelations by Joseph Fielding McConkie and Craig Ostler.
Also FYI, there is a little bit of overlap between the church history information in this book and the Church's Revelations in Context book edited by Matthew McBride and James Goldberg, but I think both are worth reading.
All in all, I would wholeheartedly recommend this book to my friends and to anyone else who wants to study and understand the Doctrine and Covenants better. Reading it helped increase my knowledge, testimony of, and faith in Jesus Christ. It strengthened my testimony of the Prophet Joseph Smith and the restoration of the gospel in these latter days.