The Library of Apollodorus

The only surviving complete compendium of Greek myth from classical antiquity — if you want to understand Heracles, the Argonauts, or the Theban cycle at their source, this is the book. It reads more like a reference index than a story, so expect utility over pleasure, but Robin Hard's translation makes it as approachable as a two-thousand-year-old myth catalog can be. An essential shelf item for anyone serious about Greek mythology.