A perfectly acceptable piece of Third Doctor froth, that (budget aside) could have slotted very easily into Pertwee's final seasons as the the Doctor. The characters are spot on, and the era is captured well. If anything, that's the problem with the book. It's too slavish, reworking common themes from Pertwee's time and placing them in an only slightly different story. Fans of the era are likely to find it all too familiar. For new readers, it's a great romp. Does it matter that the appearance of a certain recurring villain is poorly explained, or that the background of the invadiing alien horde is underdeveloped? Not really - this is a slice of seventies Who that should be taken with a pinch of salt and enjoyed for the silliness it is.