Possibly I've only imported this thought because of my knowledge that Summer Crossing was a first novel, but it does feel a bit rough around the edges in places - a sentence or an image falls in a place that strikes a subtly wrong note, or a shift to a different character's point of view jars, or the pacing seems to have momentarily skipped a beat (most notably in the last 15-20 pages or so) - but it's probably revealing that the figures of speech which have come naturally to mind in describing this novel are musical...
The writing is, for the most part, light and clean, and if it occasionally tips into over-floweriness, every one of those slight miscalculations is balanced by a moment of genuine lyricism; as far as the latter goes, this passage was the first in the novel that touched me a little (it really needs the context, but anyway):
...Whereas Peter had cared exceedingly. All their childhood she'd helped her friend build, drafty though it was, a sandcastle of protection. Such castles should deteriorate of natural and happy processes. That for Peter his should still exist was simply extraordinary. Grady, though she still had use for their file of privately humorous references, for the sad anecdotes and tender coinages they shared, wanted no part of the castle: that applauded hour, the golden moment Peter had promised, did he not know that it was now?
...a passage which takes on greater resonance in light of the novel's ending, too.
Anyway, this doesn't feel like a book to which I'll return, but it does have something - an air, an atmosphere - that I very much associate with The Great Gatsby, this sense that I can never put into words but which I feel has something to do with bright, glittering lights, beautiful people poised fragilely, and intimations of shadows at the edges...
