One of the problems is that imho it is quite unclear which book is book 4. I mean one can look at publication order sure, but that is quite misleading since most books after Baltic War are set in a particular location and have only tangential connection with the main (as it is) series featuring Mike, Rebecca, Gretchen, Emperor Gustav etc - one can argue that book 4 is actually the one authored years later by E Flint alone where Mike Stearns becomes a general leading a United Sates of Europe (or was it Germany?) army in Poland (forgot the name of the book) and its immediate sequel and which were among the better series books...