Puffin Classics has reprinted all six of Roger Lancelyn Green's re-tellings of myths and legends—and my son owns them all. We actually started with Myths Of The Norsemen prior to a trip to Iceland last year, but haven't (yet) finished it. He is currently on a huge Greco-Roman mythology kick thanks to Rick Riordan. He devoured Percy Jackson's Greek Gods in like two days.
Green's syntax is occasionally antiquated for no good reason, but otherwise these books are solid. While the worst excesses are glossed over, there is still a fair amount of questionable content which should come as no surprise to those familiar with these stories—plenty of violence, forced marriages, etc. These have sparked some good discussions with my son. Some parents might find this content understandably objectionable. On the other hand, many of those parents think nothing of such content at sunday school where it is often decreed by a God they aren't willing to criticize for it. So it goes.