BookRiot recently published a list of 50 must-read Hellenic mythology books, and it's quite a list! The list is accompanied by the following disclaimer (of sorts):

"If you’re still fascinated with Greek mythology books, or looking for Percy Jackson or Circe read-alikes, you’ll find the best of them here for adults, teens, and kids alike.

Books are broken down by category: translations of the classics, fictional retellings, nonfiction commentary, as well as books for teens, middle graders, and kids. I’ve also only included one book per author to increase our scope here. All book descriptions come from Amazon."

One note: Robert Graves. Graves is a storyteller; he spun stories based on facts he could find. If he could not find a fact, he made it up to fit the story. Because of this, his books are a great read, but they are not reliable as far as ancient mythology goes.