Valishevsky was, in a sense, the pioneer of the popular science genre, which developed only many years later as a special (and quite respected) type of literature. From the text of the book "Daughter of Peter the Great" you can see that Valishevsky, unlike many contemporary novelists and popularizers, worked a huge amount of literature and sources and, unlike, again, from some modern authors, did not hide this circumstance, setting his work as a reference apparatus.