Will Grayson is pretty average, his best friend Tiny Cooper is fabulous, and the girl he kind of likes is pretty awesome.
Will Grayson is medicated for depression, lives for the times he can talk to his best friend/online boyfriend, and generally wants nothing to do with much anyone else.
The two Will Graysons meet by chance and their lives take a turn for the interesting around Tiny and his upcoming musical production.
The authors alternate chapters from the viewpoint of each Will Grayson, providing them with unique voices. John Green's Will agonizes over his life, uncertain how he was saddled with such a ridiculous best friend, unsure of whether he wants to try dating Jane (who isn't really his type, besides he's far too stupid for her), and generally trying to get through without making waves. david levithan's will grayson doesn't believe in capital letters, doesn't think much of anybody, but is inexplicably attracted to the sprinkled donut of a person that is tiny cooper.
As different as the two of them are, they experience many of the same things: doubt, regret, betrayal, and the highs and lows of growing up.