There are a host of excellent books (grammars,
dictionaries and readers) available to those who already know a Scandinavian
language. One of the best I’ve found so far is Grunnbok i norrønt språk – ISBN
8241702124 writen in nynorsk.
For those who would rather use an English text, I
would suggest the second and third parts of a new introduction to old Norse.
These works are not completed yet but are available from the Scandinavian
Studies Department at University College London
or the Viking Society for Northern Research
Part two is a gentle introduction to a few of
the sagas, including a word for word translation, while the third part
can be used along side as a reference when needed.
Hope this helps!
Tim H