Each one explores a major theme and several subthemes. Characters and the worlds they inhabit, though richly detailed and developed, are on certain levels just tools she uses to examine and probe the major theme she is exploring. Each book can be read on one or more of these levels. In Conquest Born can be read as a simple space opera about combating generals, but it can also be read as a discussion on how men compete with each other, or on the nature of aggressive behavior, or even as an examination of the role of women in human society.
World building is another strength.
This is especially apparent with In Conquest Born , where two diametrically opposed civilizations are created with incredible detail. And unlike most authors who describe a universe in the first few chapters and never bother to develop it again, Friedman is constantly providing insight into the workings of the cultures in which her characters live. It is a style similar to Marrion Zimmer Bradley's The Mists of Avalon , wherein the culture of the protagonists is just as carefully depicted as the people themselves, to the point where the setting becomes a character in its own right. This is where a chapter outwardly written about a minor character is really meant to provide through an indirect view insights into a major character's behavior or background, and thus, his motivations. The second chapter of The Madness Season not only introduces us to Marra, but also depicts the Tyr from a second point of view completely different from that of Daetrin.