Is the great gatsby believable?

Of course. It's not a simple "realistic" novel but is a mixture of fantasy that represents reality with the trappings of social cirstance feelingly and rightly used. On its own terms--not in the light of some quotidian notion of what happens in everyday life--the book captivates and puts one there, so it is believable, the way Stendahl and ens and Flaubert are believable.