The third set of episodes in this season-length story feels more tightly bound than the previous ones - a single story all the way through, rather than four separate ones. The focus is on the initial stages of the invasion that the previous two sets were leading up to and the continuous thread keeps things moving at a rapid pace, the threat escalating as it does so.
As in the two previous sets, one of the four episodes deals with a 'classic' monster, rather than the arc villains. (It should be obvious which one from the cover). Even here, however, it's a direct part of the larger story, rather than an add-on to bulk things out. To anyone coming into this solely from the modern series, it will be new, but it's sufficiently explained that this shouldn't be an issue, and no real knowledge of the original is required.
Other than that, we have a story that hops about across the globe and beyond. Despite being a UNIT story, some of the sections take place in outer space - some of the science here is ropey, but not enough to be distracting and nothing out of the ordinary for the TV show, either. Significant sections take place in Norway, Canada, and China, albeit with the former two in wilderness areas that might as well be anywhere. (And, as a note, that's not how you pronounce 'Qing').
Along the way there are some major changes to the line-up, plenty of action sequences and perilous escapes and generally the sorts of things you'd expect from a military-themed spinoff. The collection ends on a cliffhanger, but given that it's part three of a four-part series, that's hardly unexpected.