Leinster is one of the lesser known writers from the Golden Age of science fiction, which spanned the 1940s-1960s. He was very popular in that era and very prolific, plus he also managed the feat of writing for mainstream magazines such as Argosy as well as the science fiction magazines which were looked down on as 'pulps'.

The stories are a mixture of straight science fiction such as 'Pipeline to Pluto' or more fanciful tales involving time travel by mental control. The key feature of all Leinster's work is the ethical and moral strand in it, with villains often getting their come uppance. In fact, one of his stories is called 'The Ethical Equations' and in it a lowly Lieutenant who has been put in charge of first contact with an alien species aboard a wandering vessel that has entered the solar system has to balance the needs of humanity (and the combination of greed for the aliens' technology with the desire to destroy them to safeguard Earth, shown by his superiors) and the requirement to act in an ethical way for all parties.

As with any stories from this period, the modern day reader has to make allowances for certain attitudes. There doesn't appear to be any obvious racism, but attitudes to women are typical of the time, with female characters being wimpish and irrational. One of the better stories, 'If You Was a Mocklin', is slightly spoiled by this, but is still amusing and with a good twist. Probably the best story is 'The Devil of Eat Lupton', about a tramp who makes first contact with what appears to be the scout for a hostile alien force, and deals with his complete incomprehension and blundering, and the unexpected outcome.

Regarding the cover of the UK edition, presumably a homage to the bug eyed monster sensationalism of pulp era magazines: the story it illustrates is anything but, as the BEM in question is an intelligent creature from a race which has a totally aquatic experience and carnivorous mentality. Nevertheless, this individual overcomes its mindset to interact helpfully with what to it are completely alien creatures, human beings. So Leinster actually subverted the usual pulp stereotype in this story, Dear Profundis. ( )