what next and more on definitions in novels

Cerelian Gold is heading toward climax and ending rapidly but I haven't yet decided what tale to post next, whether science fiction or fantasy and whether to try to keep to the more adult themes rather than the young adult that I post to my other blog. Part of the hesitation is that I might not actually have a choice on the latter as I don't know that I have another grown-up science fiction or fantasy ready for public viewing. I tend toward young adult quite unintentionally and didn't even know that that was what I was writing for many years, many novels. I suppose because the bulk of the science fiction and fantasy novels I was finding and reading when i got started were billed as just that, not specifically as young adult at all, but in retrospect, that's what they really were. Adding substantial romance and the psycho-drama are what really made them different in my view. I wonder what other themes make a book general or adult instead of young adult? Perhaps I will let the readers see how I explore a new idea, long before it becomes a novel... I'll take suggestions for themes.