The books you need to look at:

The Vikings by Gwynn Jones

The Varangian Guard by Sigfus Blondal

Harald Hardrada: The Warrior's Way by John Marsden

Marsden is the most readable if you just want a good glimpse into the Viking age. Harald was the last real Viking conqueror and my god he was good at it. It's a tragedy that the only thing people remember is his defeat in 1066 by Harald Godwinson (who then lost to William the Conqueror it was a really BAD YEAR for England ok).

Things you need to stop thinking about Vikings:

- They were dirty and stupid and illiterate (some were, of course, but not all of them)

- All girls all the time were shieldmaidens (no, actually: RICH GIRLS were shield maidens. They had to pay someone to take over their wifely duties of running the household while they were out Viking. But YES lots of girls could kick your ass six ways from Thor's Day with weaponry. But being trained to fight is not the same thing as being a shield maiden. SO STOP THAT). More on that from Gwyn Jones up there.

- Dark Ages girls had no rights. No, actually they had A LOT OF RIGHTS. Girls could be queen, girls could topple empires, girls could reign Byzantium, girls could lead a freaking army, could do anything a boy could do... The whole resurrection of the strict patriarchy actually came later into the middle ages and renaissance. The Vikings held equal primogeniture to a large degree; they'd never understand a strict patriarchy- and they'd be the first one to disbelieve any girl was a helpless fragile flower. The actual reason they would run around murdering an entire town ok? They figured the women could fight just as well so kill them to be safe.

- Absolute monarchy had absolute control No. No it didn't. Even the Byzantines were forever fighting their own rebellious generals and stewards and armies. So that is how the Vikings could swoop in and cause YET MORE CHAOS.

- Vikings were limited to the ocean. NOPE. Those longships work hella well in rivers. And streams. And are easily carried overland if need be. So guess what: wherever there is water THERE MAY BE VIKINGS. Now, Dark Age Peasants, let's see you sleep well tonight...

This is your random medieval blurb for the day.