Certainly these Venusians can be called alien
This is, I think, is the second of the Missing Adventures series (though Goodreads says that it is the third). These series of adventures occur between various episodes of the older Doctor Who series and use the original Doctors and respective companions. This one sees us return to the first Doctor and two of his companions: Ian and Barbara (who where two of the three original companions, the third, Susan, having left in The Dalek Invasion of Earth).
The Doctor decides to take Ian and Barbara back in time a very long way to when the Universe was much younger to visit the Venusian people who once inhabited the second planet of our Solar System. However this far back in time things are much different. The sun is smaller and Venus is still habitable, albeit barely. The people of Venus (strange reptilian aliens with multiple legs and tentacles, an image of them is on the front cover) are generally a peaceful people but, as they are facing the disaster of their world being destroyed as the sun heats up, are looking for ways of escape.
The Venusians have a number of options including simply accepting fate and dying. They also propose to move beneath the surface of the planet, erupt volcanoes to send dust into the atmosphere and cool the planet, or migrate to the currently uninhabited third planet. During the adventure some more aliens rock up saying that they will assist the Venusians in their plight. However this is all a deceit and it turns out that they simply wish to use the Venusian's as food.
This is an interesting concept that is raised here, and that is the concept of eating one's dead. It has been explored in Stranger in a Strange Land and is also explored here. The idea is that when one dies, the friends and family then choose to consume the corpse, not out of hunger but rather because by doing so the belief is that their soul is absorbed into those participating in the meal (and there is actually such a ceremony, albeit symbolic, that is practised in one of our world's major religions). In a way it is a means on remembering the fallen. However this is an alien culture (and I am not aware of any peoples practising this ritual on Earth in the 21st century beyond a symbolic form, however that does not mean that it does not happen, nor has it happened) and when we come to alien cultures in a science-fiction setting, the rules change. In fact the rules are limited only by what the author allows them to be. On Venus, when one consumes the dead, as Barbara inadvertently did, they obtain their memories, and to some extent, their gifts as well (such as oratory in Barbara's case). I will not go any further into this concept though because it is not a part of our culture, but we need to be aware that the idea is out there.
The second idea that arises from this book is the idea of desperation. When all seems bleak, we tend to resort to extra-ordinary actions. As the sayings go, 'desperate times call for desperate measures'. However this should not be a justification for anything goes because it can end in disaster. The Venusians have a number of options, but the options that they take involve trusting an alien race that turns out not to have their best interests at heart. Once again we have the concept of food, but it is different in this case because the aliens see the Venusians as not of their kind, therefore okay to eat (however do not understand the nature of what happens when one eats a Venusian). In the end the simpler solution, which gave them another ten thousand years of life, was the better solution (they could have left the planet, but due to their allergy to metal, this was not possible).
Finally, I noticed that in the books, once again, imagination is the only limit. In the original books, the aliens were generally (not always but generally) limited to bipedal humanoid creatures. That is because computer imaging and special effects were very limited and very expensive, and Doctor Who hardly had a huge budget to work with. However in the books it is much easier to be more creative, especially with the creatures, and this is what has happened here. Also, I note that the authors are also beginning to experiment with alien names.
