A kind of random collection of stories, Tales of Long Ago includes both Greek myths and the Arabian Nights. I've read a version of the Arabian Nights but know embarrassingly little about Greek mythology so I have no idea how accurate these stories are to other versions not for kids. I imagine they have been quite watered down!
It's fairly Blyton-esque, funnily enough similar to some of the other short stories I've read from her, but instead of pixies and brownie and naughty kids, we have gods and goddesses and merchants and genies. Most of the Greek mythology stories are morality based tales, or "this is why things are the way they are."
Probably a fairly enjoyable intro to these worlds of stories, but plenty of slave-talk and other racist elements, unfortunately but not surprisingly.