hi stunted,
my novel is literary YA. It was never an explicit choice -- I just always meant to write a book with many layers, and my natural voice just comes out more literary.
tone is one of the main elements that sets literary apart. but boy, is that term ever hard to describe. in literary, there's more introspection. a slower pace. more description, more expository. an overall deeper feel, which should be apparent from the very first pages. and yes, they usually take longer to read and write -- there's more crafting involved (someone might jump in and argue against me, but I stand by it) right down to a word choice level, somewhere in between writing a scene from a snappy commercial book and a poem. more subtlety. more use of those literary devices you learned in high school -- I had so much fun with symbolism in my book.
almost anything that wins the Printz is literary, at least somewhat. YA books that are undeniably literary are Jellicoe Road, A Certain Slant of Light, Bog Child, The Book Thief, Madapple, Tender Morsels, and the Octavian Nothing duo. there's a vast gray area, for sure. Books like Story of a Girl, Looking for Alaska, Before I Die, etc. really straddle the line of commercial and literary (which is what I hope my book does).
Pitfalls: the main one is including so much description, introspection, and other detail that it bogs down the story. Adult literary can ramble on forever, because in general, grown-ups have a longer attention span than teenagers. But that's why YA literary can be so amazing -- by nature, even the most literary YA book is quicker and more commercial than literary adult books.
hope this helps!
