Atalanta and her foster father are hunting in the woods when they first realize they are being stalked; within minutes they are running for safety from a beast the like of which neither has ever seen before. Atalanta arrives at their cottage unharmed but her father, who paused to throw a spear at the beast as he fled, was savagely gored and is dying of his wounds by the time he arrives at his frantic daughter's side. With his dying breath, he gives her a ring and tells her of how it was on a cord around her neck when he first found her in a she-bear's den- doubtless a final gift from the family that abandoned her.
I remember reading Hippolyta and the Curse of the Amazons in preparation for our library's Battle of the Books when I was ten- I expected to hate it, but I loved it. I went on to acquire my own copies of all of the other books in the series. For a very long time they were my favorite books- I read them with my father and shared them with my sister.
These books were written for people aged twelve at the oldest, so that's who I recommend them to, but they are still good if you're in high school.