Reddit reviews The Gods of the Greeks

Well, there's The God of the Greeks by Karl and Carl Kerenyi. Papa Karl is one of the best respected scholars of classical mythology of the last century, so that's a good way to go.

Robert Graves' The Greek Myths is exhaustive, but I'd only recommend it with a few caveats. One is that the nature of his project tends to bastardize the stories a bit -- he wrote the book as a way of unifying the myths, but the very nature of Greek myth is that it's various and contradictory. Graves gives a very readable (and thus popular) account, but it isn't without flaws.

For something a little more classical, check out Erwin Rohde's Psyche, one of the pivotal 19th century texts of mythological scholarship. Rohde was a contemporary and friend of, as well as influence on, Nietzsche, and his ideas greatly informed the development of classical psychology. This is more specialized stuff, but it's interesting and gives a bit more insight into Greek religious thought than you would get from reading the myths alone.

If you're interested in the 'rarer' and more obscure Greek myths, try to find copies of The God of the Greeks and The Heroes of the Greeks both by Karl Kerenyi. He does an amazing job pulling many of the Greek myths into a very good narrative and really focuses on a lot of the lesser known stories or versions of stories, many which I've not seen referenced outside the source material.

Karl Kerenyi: Dionysos: Archetypal Image of Indestructible Life

https://www.amazon.com/Dionysos-Archetypal-Image-Indestructible-Life/dp/0691029156/ref=sr_1_3?ie=UTF8&qid=1467401166&sr=8-3&keywords=kerenyi

Karl Kerenyi: The Gods of the Greeks

https://www.amazon.com/Gods-Greeks-Karl-Kerenyi/dp/0500270481/ref=pd_sim_14_5?ie=UTF8&dpID=51fE0nLHjeL&dpSrc=sims&preST=_AC_UL160_SR108%2C160_&psc=1&refRID=AGC3MSCM73V53NBM0SHD