In many ways this is the book that the previous 4 have been working up to, as we encounter the Daleks who've been foreshadowed from the word go. In a very back-to-Skaro moment the Doctor is captured by a bunch of Thals who have a mad scheme to force Davros to turn them into something that can defeat the Dalek threat. The Doctor, of course, argues against this but is, naturally, overruled. Fortunately for all the Imperial Daleks intervene before things can go even worse for the Galaxy.
This book also features one of the silliest retcons I've seen; in which it is shown that the Hand of Omega did not, in fact, destroy Skaro but an innocent planet nearby!
On the other hand, this is a much better Doctor than we saw in Genocide and the Thals are convincingly portrayed has having become almost as soullessly bad as their long-time enemies the Daleks.