The Vinland Sagas are great, and they can be found on their own, as part of larger saga collections, or online. I always recommend looking for a more recent edition, since some of the old ones (including the 19th-century translations that often pop up online) can be tough to read. I've often found the Penguin editions suit me best in terms of translation and price, and they're often equipped with excellent scholarly introductions.

But the Vinland Sagas are not, of course, history books, so if you're looking for the actual history of the Norse diaspora across the North Atlantic, you'll have to look further afield. I'm personally a big fan of James H. Barrett, ed., Contact, Continuity, and Collapse: The Norse Colonization of the North Atlantic (Turnhout, Belgium: Brepols, 2003). It's expensive (at least through Amazon), so I'd strongly recommend asking your library to get you a copy. University and public libraries alike should be able to do that within a few days to perhaps a week or two.

Of course, the Norse diaspora also figures largely in a broader variety of books as well. Viking Empires, The Oxford Illustrated History of the Vikings, and Vikings: The North Atlantic Saga are all good reads. The last one is from the Smithsonian and has a companion website; it might be worth poking around a bit.