Short answers, pulled from the story.
Frans Gunnar Bengtsson wrote The Long Ships between 1941 and 1945 while Nazi Germany occupied much of Europe. He based the story on historical sources including Snorri Sturluson's Heimskringla and old Icelandic literature.
The novel follows Orm Tostesson from Scania who joins a Viking raiding party led by Krok to travel to Muslim-controlled Andalusia in 982. The narrative contrasts pragmatic Norse paganism with Christian and Islamic doctrines while weaving actual events like the Battle of Maldon into its fictional storyline.
The first part of The Long Ships appeared in Swedish in 1941 followed by the second part in 1945. Each section contained two books making up four volumes total for the original Swedish release.
The book has been translated into at least twenty-three languages since its initial release. It once stood among the most widely read books in Sweden throughout the mid-twentieth century.
A British-Yugoslav film titled The Long Ships arrived in theaters in 1964 starring Richard Widmark and Sidney Poitier. That production retained little more than the English translation title and Moorish settings from the source material.