There was a time when this was literally the only Doctor Who book in existence (under its excellent original 1964 title of Doctor Who in an Exciting Adventure with the Daleks); indeed it was the only commercially available representation of any Doctor Who story, in those days long before video-recorders (let alone DVDs). So we have Whitaker taking much greater liberty with Terry Nation's TV script than almost any other novelisation (John Lucarotti's treatment of The Massacre differs even more from the story as broadcast, but he was reverting back to his own original script).
And the result is quite possibly the best of the novelisations, judged as a novel. The opening of the story is comprehensively rewritten, Ian being an unemployed research scientist who accidentally encounters Barbara, who has been tutoring the mysterious Susan, and gets involved with the Doctor and his Tardis. So much time is invested - wisely - in setting the scene that we are a third of the way through the book before we reach the equivalent point to the end of the TV story's first episode (out of seven).
The biggest novelty, for those of us who have read almost any of the subsequent hundreds of Who books, is that the whole story is told in the first person, from Ian's point of view. (It's not unknown in later Who literature, but it is very unusual.) This does require a certain amount of narrative juggling, but Whitaker gets away with it better than I remembered from when I first read this, three decades ago.
Today's generation of fans will squee at the pronounced sexual tension in the Ian/Barbara relationship here - the TV story has Barbara close to flirting with Ganatus, one of the Thals, but he barely gets to look at her on the printed page. Poor Susan rather fades into the background as well after she has done her mercy run to the forest. The characterisation of the Doctor is much more harsh and edgy than Hartnell's depiction; since Whitaker was the story editor, perhaps this was what he had originally in mind? (A possibility supported by the surviving first cut of the first ever episode.)
And the Daleks themselves are pretty memorable here, though Whitaker seems a bit confused about their size - three feet high at one point, four foot six at another, though the illustrations are of our "normal" sized pepperpots. However, this confusion is compensated for by the glorious description of the mutants within the metal casings, and their glass-enclosed leader. The TV show has never managed such memorable presentations of the creatures inside, though it has occasionally tried. (The versions encountered by the Ninth Doctor come closest.)
Anyway, this is an excellent read, well worth hunting down.