For something fantasy related, I'd recommend the
Acacia Trilogyby David Anthony Durham. I really feel it's one of the most unique fantasy series to come out in recent years, but it's sadly not gotten the recognition it deserves. It also has the advantage of being a finished series, so you don't have to sit around and wait for the next book to come out.
For something more along the lines Stephen King, I'd suggest checking out Dean Koontz. He considers himself a "thriller" author more than "horror", but most of his books straddle that line. However, I'd suggest starting with his earlier books and avoid anything written after 2005 as he's seemed to have lost some steam in recent years (particularly with his obsession over Odd Thomas).