Much like the episode that inspired it, Galaxy Four is a thoroughly uninspiring, frequently boring, and utterly repetitive novel. That's not to say William Emms did a particuarly bad job - he just failed to elevate the already weak source material. The Doctor, Vicki, and Steven all arrive upon a planet in it's final death throes, uninhabited except for two crashed spaceships - one occupied by the violent, aggressive, yet beautiful Drahvins, the other by the seemingly peaceful, yet apparently horrifying-looking Rills. Of course, this being a Doctor Who novel, whilst the Doctor could decide to just leave this godforsaken rock, he gets caught up in the conflict and various circumstances just happen to pop up to stop him from getting the hell of this nigh-doomed planet.
Up until the last moments of the books, the death of a planet has never felt so unimportant, when more time can be spent critiquing the women's rights revolution in the form of the beautiful, yet threatening (and frequently bumbling) Drahvins. Seriously, this books goes out of it's way to describe Maaga (interesting name, in today's times) as beautiful, dangerous, nightmarishly evil and utterly bigoted (both towards men and the Rills) at any chance it gets. Throw in some pretty basic ideas about not judging people by how they look, Galaxy Four doesn't really do anything particularly interesting, though I say this with the benefit of reading the book nearly forty years after publication.
The writing around the Rills, their genuinely gentle nature, and any description regarding the antics of the Chumblies are a highlight, but they do little to offset the boring, repetitive descriptions of the Drahvins. The book does kick into a decent high gear in the last few pages, especially in regards to Maaga's last stand, but by then, I was pretty much checked out.
Galaxy Four isn't atrocious, but an already weak story doesn't help this adaptation. Read it for the Rills and the Chumblies, or if you can't stand the audio or animated versions of the story - otherwise, there are literally dozens of other Doctor Who Target novels to better occupy your time, as Galaxy Four would rank pretty lowly in my personal selection.