Book reviews are written at the time of a book's release; they are a good way to understand the book's initial reception by educated readers. In a review, the book critic may assess the book's literary merits and flaws; consider how it relates to similar books by the same and other authors; and/or recommend whether others should read the book.
The databases listed in the box below are all good sources for book reviews. To find them, you may want to construct a search that looks like this. The quotation marks around the book title tell the database to search those words as a phrase.
"when the emperor was divine"