The biggest problem I found with the book is not what it does—indeed, I thought is expertly delivered in most of what it attempted—but what it claims to do. In the introduction, Brown claims that this book is not only a work of historical theology, but also of lived religion. Indeed, he claims that in the case of Mormonism there is little distinction between the two. While much of Brown's approach does indeed incorporate elements of lived religion—a methodology of growing significance in the academy, but woefully underused in Mormon Studies—it would be a stretch to make the distinction Brown does due to the narrow focus of the volume.
This overreaching emphasis is further demonstrated in Brown's belief that "the leader is often difficult to separate from the followers" in early Mormonism, and thus it is not only possible but also necessary to "consider them together"; later, he writes that "boundaries between clergy and laity are highly permeable" in the LDS tradition (306). This approach seems poised to perpetuate the top-down model of early Mormon history, claiming broader relevance for what is actually a narrow subject group. This focus is not bad in itself, especially when as skilfully handled as in this monograph, but it can be misleading when framed in a way as Brown's introduction.
Other competing views and writings by John Taylor, Orson Spencer, Lorenzo Snow, or the Pratt brothers, not to mention the thousands of average members who privately lived and interpreted their new-found religion are discarded or ignored because they don't fit the framework of Joseph Smith's cosmos.
But my problems with the framing of the book should not take away from the overall value of the volume. All historians of early Mormon thought must come to terms with Samuel Brown's remarkable scholarship, which should prove to be foundational for all future work on Joseph Smith. Exhaustively research, creatively imagined, and powerfully written, In Heaven as it is on Earth is prime evidence for the maturation of Mormon Studies.