I reviewed this classic SF tale on this blog over eight years ago, but as it has recently been the book of the month for the Classic Science Fiction discussion group ( https://groups.io/g/ClassicScienceFiction/topics ) it is worth reviewing in the light of points raised in that discussion. First, extracts from my review from 2010:
This novel, first published in 1965, was one of my favourites from the period and I still have my well-worn 1967 paperback. It's several decades since I last read it so I thought I'd see how it stood up today.
I've already posted one review of a novel by this author (A Trace of Memory, reviewed 15 December 2007) which I started as follows:
"Keith Laumer (1925-1993) was a prolific American SF author who specialised in fast-paced adventure stories (of which the Bolo series, concerning intelligent tanks, is best known) and comic satire, notably in the Retief books about an interstellar diplomat. A Trace of Memory, published in 1963, is a stand-alone novel in the former category."
A Plague of Demons falls into the same category, being a short (170 page) and exciting adventure thriller. It is set on a near-future Earth and features a government agent, John Bravais, who is tasked with investigating the mysterious disappearance of large numbers of soldiers involved in the formalised battles then being used to settle disputes. He observes a dog-like alien - one of the demons of the title - decoying soldiers away from a battle and attacking them. He is able to kill one of these extremely tough creatures and take back evidence of its alien origin. His task then becomes the investigation of what is going on, and to assist him he is given a new programme of internal biomechanical enhancements which greatly increase his strength, endurance and survivability. The demons are quickly on his trail, assisted by their ability to manipulate people's minds so they can appear to be ordinary humans, and what follows is a running battle which ends up off the Earth as Bravais desperately tries to fulfil his mission against heavy odds. I can't say more without spoiling the surprises for any new readers, but I will say that this is the book whose popularity inspired the Bolo series.
The story is told in the first person with the laconic hard-boiled style of a Mickey Spillane thriller, including one-liner gems such as: "I was as weak as a diplomatic protest". There is also something of the flavour of Eric Frank Russell's novel Wasp, reviewed here on 26 August 2007. The introduction in particular reminded me of the start of a James Bond movie - I could visualise the film scenes as I read. In fact, the whole book would make a good film, with little need to change anything. Inevitably, the complex plotting and character development which feature in most modern novels are notable for their absence, but in this kind of story they would only slow the pace.
Some of the issues raised in the discussion group have wider implications for the way in which we read and appreciate SF – especially the classic variety – so are worth exploring.
One complaint is that the story is set in a future (date unspecified) in which the general technology level seems not very different from ours, but there are some improbably advanced exceptions (e.g. medical science, recovery speed from operations etc). This surely should not be a surprise, something like it happens in reality. If it were possible to bring SF fans from 1965 into the present day, they would be astonished: blown away by the amazing capabilities of gadgets like smartphones, but appalled by the number of expected developments which have not happened. Where is the free nuclear fusion power? Why haven't the computerised production machines freed people to work only part time? Where are the permanent bases on the Moon and Mars, or the manned explorations of the outer regions of the Solar System? Why are we still lumbering around in subsonic passengers jets when in 1965 the Mach 2 Concorde was on the drawing board – surely we should be using hypersonic planes by now? Where are the very high speed maglev trains intended to revolutionise ground transport? Why aren't flying cars or strap-on jetpacks not routine forms of transport? Even worse, travel on our urban roads is often slower than in their time due to the traffic densities.
Progress is always uneven, and can happen in unexpected areas, while expected developments often fail to happen at all and most things only evolve very slowly. And the further you are down the socio-economic scale, the more slowly your life changes.
Which raises the wider issue of what we are prepared to believe (or not) in SF. Some suspension of disbelief is almost always required (with the exception of Mundane SF, in which anything beyond known science is banned), but we are notably inconsistent in what we are prepared to accept, and what we are not. Logically, developments which are contrary to some fundamental laws of science as we understand them should be the hardest to accept: that would obviously include faster-than-light spacecraft (that's most of SF wiped out in one blow); time travel; and anti-gravity. It also includes "psi powers" beyond human capabilities (goodbye superheroes!). Next would come capabilities which are not contrary to scientific laws, but which we really can't see any way of achieving for now (that's most of the rest of SF gone, particularly anything with an AI capable of exceeding the capabilities of the human brain in all respects). Finally come things which we can't do now but can see a path to doing in the future (that's the Mundane stuff, like setting up a base on Mars). In practice, though, people sometimes seem more ready to accept "impossible" things in a story rather than those which are merely improbable.
So, to return to A Plague of Demons. It includes alien empires with FTL spacecraft, and an anti-gravity harness (not alien; made on Earth). But what has caused more comment (apart from the medical capabilities mentioned above) are issues like the ability of Bravais, trapped in his massive battle tank, to regain consciousness, make mental contact with the aliens and even control some of them. (For the record, the consciousness bit is explained earlier in the story, the result of hypnotic mental training to split off a personality fraction so that Bravais can see the Demons for what they are, while the mental contact is initiated by the aliens – it is their method of command and control – but it turns out to be a two-way system that Bravais can utilise.)
What it comes down to, in my view, is that if you are really enjoying a story you will be prepared to suspend disbelief as far as necessary and to swallow almost anything the author gives you. If you don't like it, then it's not difficult to pick lots of holes in it, because most SF relies on the suspension of disbelief to work at all.
All in all, I see nothing here which is out of line for this type of fiction written at this time, and no reason to change my previous verdict:
I can well understand why I liked this book so much and can warmly recommend it to readers who enjoy the style and pace of these 1960s SF thrillers. It's such great fun, with an added dash of nostalgia!