Intriguing premise from the get-go: aliens land in 12th century England, to be precise, in a small barony preparing for the war in France. Lasers vs. lances, you'd think the outcome foregone. Wrong! The English slaughter the invaders! Then the baron has this brilliant idea of using the spaceship to ferry troops to France, then on to Jerusalem, but ends up conquering outer space instead. Hilarity ensues.
Behind the blustery antics and space opera lie two serious topics, and it's quite a wonder how Anderson handles them. First is Anderson's commentary on social structures; understandably, the feudalism of the English knight gets a leg up over the supposedly-egalitarian society of the Wersgorix. Wersgor society sounds a lot like the society we idealize:
But no one was born to his place in life. Under the law, all were equal, all free to strive as best they might for money or position. Indeed, they had even abandoned the idea of families... Male and female seldome lived together more than a few years. Children were sent at an early age to schools, where they dwelt until mature, for their parents thought them an encumbrance than a blessing.
The Wersgorix had no special affection for their birthplace; they acknowledged no immediate ties of kinship or duty. As a result, each individual had no one to stand between him and the all-powerful central government.... The Wersgor were a lickspittle race, unable to protest any arbitrary decree of a superior. "Promotion according to merit" meant only "promotion according to one's usefulness to the imperial ministers."
Second is how Anderson handles religion. Though at first it appears that he makes fun of faith and prayers, in the end, he portrays it with deep sensitivity that's rare in scifi novels. But you'll have to read it to understand.
I picked this title up some weeks back in the Book Sale bargain bin; pretty good quality still, and at P45, a steal. And hey, it's Poul Anderson. He always delivers a good yarn, "Three Hearts and Three Lions" being at the top of my list. It will probably have to make way for High Crusade.