Highly derivative SF from the mid sixties. It owes a significant debt to the Foundation trilogy. The writing is awful and the characters are flimsy. There is one named female character, who does nothing significant. Both authors would go on to write somewhat better stuff individually. ( )

This was the novel that turned me onto science fiction, and it illustrates the fact that SF works at all sorts of levels. I read it at the age of ten, when we were holidaying in a caravan in North Wales and I came across this book, but the cover was missing. I never knew what it was for years...

The plot: an Earth ship encounters the vanguard of an expanding alien force in deep space. They are able to defeat the aliens, but find that their invading forces are ten years behind. In their way is a world in a roughly medieval stage of development. The 'Prime Directive' prevents direct intervention by the humans, so instead they infiltrate the planet's society and begin shoving like mad to take them from knights in armour to technologically-advanced starflight in ten years so they can fight off the aliens themselves.

This novel stayed with me for years due to one image - a group of nobles, dressed in roughly 17th-century Cavalier-style clothing, attending comparative trials of different spaceship propulsion systems. What of course I totally missed at age ten were the satirical and earthier sides to the novel - the Sisterhood of Mother's Little Helpers in the Street of Many Flowers, for example, went completely over my head and a good thing too! And of course, there was a twist in the story right at the end which I didn't really grasp until much, much later.

This is otherwise an unremarkable 1960s SF novel, with no great pretentions to literary greatness. But as an example of the ideas that the genre can just throw off without even trying, it's perfect. ( )

The aliens are coming - in 10 years. And the only thing standing between them and Earth is the small world of Lyff, not even in the industrial age yet. But a small team of specialists is going to change that... whatever the costs.

Cramming centuries of progress into 10 years - that seems impossible, at best. But in TYTD, you will believe it can happen. The world Anderson and Kurland created is incredibly detailed and thought-through, which is especially surprising given the length of the novel. Put in an interesting story, humor and a superb sense for language, and you will wonder why this gem is out of print. If you don't know it, get it. If you have it, share it with friends. ( )