The Fifth Doctor novels have rather a good strike rate for me (the audios even more so). This confirmed the trend: a sequel to the Fourth Doctor's TV story Planet of Evil, with the Morestran empire, centuries later, destroying itself by experimenting both with anti-matter and harnessing the kinetic energy of the planets, at the same time riven by internal conflict between church and state. Messingham's concepts of anti-matter and planetary kinetics are pretty disconnected from actual science, but faithful enough to the spirit of the story which he is sequelling (and improving on). We have, as so often in Fifth Doctor novels, a rather good Nyssa storyline as she goes off investigating with dire consequences; Tegan is less well served. The Doctor here is somewhat damaged from his previous encounters with anti-matter (including Omega) which also takes the story in interesting directions. The Morestran politics are somewhat improbable but well told. I recommend this one.