My novels build on simple yet fantastic concepts: dreams you can control, reincarnation at death, reality shifts, etc., but are set in our one and only world, with all of it's imperfections.  Belief isn't required. Believe or doubt as you will. Stories have lots of room for imagination and even wishing. What do you think happened next? What should happen next?  I leave the future open to possibilities.  If being twenty-something isn't hard enough, try it with nightmares that are real or death that isn't final.  You get the idea.
My characters appear on the page and tell me where they want to go.  Most ignore my advice and make their life more complicated.  Sometimes they figure it out and sometimes they don't . 
Full-length novels need a commitment to read. There's no guarantee that the ending will leave the young characters any better off, so feel free to abandon the effort whenever.  No apologies for crude language and sex - these are books for grown-up minds if not always in grown-up bodies.