One of the most famous of the Icelandic Sagas: it was written in the 1200s in medieval Iceland, but describes existing folklore of the Viking culture that were familiar to everyone in the society. The events are perhaps based off real people but would have taken place several hundred years prior, in continental Europe. It compiles together a bunch of poems into a coherent story, and inspired a lot of popular culture references.
The story describes several generations of the Volsung family, where all members are extraordinarily brave. There’s a lot of characters and fighting between them, especially revenge against another member of the family, and their relationships get quite complicated. To give an example of a part of the saga, at one point the king Sigurd, after slaying a dragon and gaining wealth, courts two women: his wife Gudrun and another Brynhild who thought he was someone else. When Brynhild finds out, she gets Gudrun’s brothers to kill Sigurd. Then Gudrun is forced to marry King Atli (Attila the Hun).
Although only 80 pages, it was quite dense and hard to read, and I used the help of an audiobook to get through it. The translator Jackson Crawford is a professor of Old Norse and has a YouTube channel and served as a consultant for Frozen. The language of Old Norse is almost identical to Modern Icelandic so Icelandic people can read it in the original text without much difficulty.
The saga definitely felt very “Viking” — men were expected to be very brave, kill snakes without a blink, die in battle without fear, etc. They also cared a lot about honor, not just individually, but within a family: a lot of fights happened because someone wanted to avenge their father or brother and kill a son in the other opposing family.