Bullfinch's Mythology is okay; I read him for nostalgic reasons. Very dated, though charming.
Edith Hamilton's stuff is, well, not so great. Okay for kids I guess, like Butters.
Robert Graves' The Greek Myths is interesting, but idiosyncratic and a bit cranky. His pet theories are regurgitated over and over again.
In my opinion, among the best resources for Greek mythology are the following:
- Early Greek Mythology, Gantz
- Classical Mythology, Morford
Both of these are fairly massive resources, highly detailed; very updated and like most reference books are far better used in a digital environment.
~Butters 