I'm reading another one of these, and I'm trying to come up with a definition:
Wealthy young people* slumming in European capitols in genteel poverty**, experiencing the local culture*** while pursuing artistic endeavors**** and engaging in earnest relationships***** that turn into tragic lifetime memories******. Also, somebody dies*******.
*They don't think they're wealthy. Often they think they had a middle class upbringing. Until they explain their boarding schools, vacations, and ponies. Mummy sitting in the drawing room smoking all afternoon, for example.
**Genteel poverty in that they have small apartments in bohemian parts of town, but never have to work and never run out of cigarettes and alcohol.
***These folks live in the "real" city, and some of their best friends are locals. Mockery of the clueless foreign tourists is a necessity.
****They are painters, photographers, novelists, poets, whatever. The writers only write longhand and the artists never need supplies. Whatever they do, it never interferes with their free time.
*****Lots of sex, and sex very soon after meeting the partner(s). Remember, these are young artists.
******Because we know these relationships can't last, right? Because then it's not literature. It's a romance. Nobody wants to explain this lost summer to the grandkids.
*******Might be one of the lovely young couple, but often as not is the friend who chases the art thing a little too hard. Alcohol, drugs, random behavior, suicide, something gets him. This is the death that tells our lovers that the dream cannot last. That they may have to go home and get a job. One of the two (usually, if one is a novelist, it's that one) will succeed with the art part, but love will never be the same.
Note that this genre does not seem to work with actual poor people, particularly Americans, because they have to start paying off their student loans and can't just biff off to Europe or wherever.