Hades was the god of the dead, who ruled the place where dead people went after they died (Sometimes people also called the underworld “Hades”). He is a rather shadowy figure in more ways than one, spooky and cruel, and the Greeks didn’t like to talk about him too much. There aren’t that many pictures of Hades either. Generally people who had good intentions did not sacrifice to Hades either. People sacrificed to Hades when they wanted something bad to happen, like if they were trying to get revenge on an enemy.
When they did, instead of burning the fat and the bones so the smoke would go up to the sky, instead they poured blood into pits or ditches dug into the ground (as in the part of Homer‘s Odyssey where Odysseus visits the Underworld).
Persephone and the Pomegranate: A Myth from Greece, by Kris Waldherr (1993). . Not cheap, but beautifully illustrated.
Myth-O-Mania: Have a Hot Time, Hades! by Kate McMullan (2002). – a “cool” retelling of myths from a different point of view.
D’aulaire’s Book of Greek Myths, by Edgar and Ingri D’Aulaire.
Greek Religion, by Walter Burkert (reprinted 1987). By a leading expert. He has sections on each of the Greek gods, and discusses their deeper meanings, and their function in Greek society.
Aspects of Death in Early Greek Art and Poetry, by Emily Vermeule (1979). She’s an expert on early Greece, and this book goes into detail about what the Greeks thought happened to people after they died. For adults.