Does anybody know any good resorces?

There is no textbook as far as I know. When I do the lessons on that site, I always use wiktionary and this Icelandic-English dictionary (http://digicoll.library.wisc.edu/cgi-bin/IcelOnline/IcelOnline.TEId-idx?id=IcelOnline.IEOrd) to look up unfamiliar vocabulary. They left English out for a reason; you're meant to draw conclusions about the vocabulary and sentence structures from the context. As long as you have a dictionary handy for words that completely stump you, the lessons shouldn't be problematic.

I also use an Icelandic workbook called Hitt og Þetta. The PDF version is on the Námsgagnastofnun website (http://nams.is/) for free. Just type the title into the search bar that reads "leitarorð."