All cultural trends cycle through history. Long form works in verse are no exception.
They were big in Sumeria: think Gilgamesh. They were big in classical Greece: think Homer. They were big in Elizabethan England: think Shakespeare. And, they were big two hundred years ago: think Byron.
Now, they are back, mostly in the teen fiction aisle of your local book store or library. One recent one is the new novel by Stefanie Lyons, Dating Down (2015). It, and its companions in the genre are not Gilgamesh, Homer, Shakespeare or Byron. But, you've got to start somewhere. This genre has been so frozen for so long, it will take some time to recover.
Intellectual historians hypothesize that writing in verse may have originally been a mnemonic aide when most people were illiterate and fiction was strictly an oral tradition. Shakespeare and Byron were, in part, trying to imitate classical Greco-Roman forms in the process of trying to reinvent high culture that had been dormant during the Dark Ages.
These days, teen fiction aimed at girls is in verse because it is emotionally intense, while also being cute. It also captures the modern folk practice of keeping a poetry journal in lieu of a more conventional one, which is a favorite of introverted, emotionally intense bad girls across America these days. It conjures the creative spirit of all of the great manic-depressive wunderkind who die young after leaving their mark on our collective soul.
The trouble is that modern long form works in verse tend to be poetry collections loosely connected together to provide a narrative, rather than actually containing any really lengthy individual poems.
Why is this a problem?
Well written long works in prose can be page turners, flowing seamlessly as they pulls you ever forward towards a conclusion.
In contrast, a long collection of related short poems invites you, indeed almost urges you, to stop, reflect, and put the book down every two or three pages when an individual poem concludes. It's like watching a TV show with a commercial break every three minutes. While individual poems may suffice to tell their part of the story, and even to tell it better than prose would, it interrupts the flow of reading to invite your reader to interrupt the experience. This makes it much harder to finish reading the whole thing.
This isn't to say that there is an insurmountable barrier to a return to long form works in verse. Some very successful and acclaimed short novels are written in prose so carefully crafted that it reads almost like poetry. The Bridges of Madison County (1992) by Robert James Walker, and Plainsong (1999) by Kent Haruf, exemplify that literary style. And, most of the millions of English majors in the country today are very familiar with the historical forms of the genre from Gilgamesh to Byron, so plenty of potential lyric novelist are equipped with the basic tools needed to single handedly revive the form.
Until then, you can read the decidedly less than epic lyric novels that have infiltrated teen fiction at your own risk. But, don't blame me if you set these novels down before you are finished and never get back to them.