[histories]

The gold standard of Icelanders Sagas is: https://sagas.is/vara.php (love for the little old website). It's complete, as it contains all the sagas and tales.

This is a good selection from above: https://www.penguin.co.uk/books/53454/the-sagas-of-the-icela... (notably missing: Njal's Saga, but that's also available separately).

There are more sagas, though. Just not of the Icelanders.

For example the saga of the Volsungs.

If you are interested in general norse mythology then yes, Gaiman's book is really nice. The Prose Edda and the Poetic Edda are primary sources and not a difficult read.

Everything I mentioned (except Gaiman's) is published by Penguin and is a good translation.