While not technically young adult or Sci Fic/Fantasy, the Agent Penderagst series by Douglas Preston and Lincoln Child makes for some fabulous reading.
The reason I’m adding it here is because each of the books has something of a supernatural flavor to it. There is something other-worldly about Agent Pendergast. He is neither supernatural, nor mortal. And the mystery and suspense these two men infuse into their books is just…amazing. I’d love to be able to weave plots as complex as these. The DaVinci Code is a picture book in comparison. (And yes, the slant pun was intentional.)
Along with Agent Pendergast, there has grown another cast of recurring characters who revolve around Agent Pendergast. These include D’Agosta, a New York cop with an intellect that, in its own way, rivals Pendergast’s. There’s also Bill Smithback, a reporter for the New York Times that is both a help and hinderance to Pendergast in certain situations.
Those are the two I can think of off the top of my head. There are others. Like some of the staff at the Museum of Natural History in New York.
Even though most of these characters originate from New York, the books to not stay there. They range all over, from the lonely corn fields of Nebraska to a secluded castle in Italy. They are truly wonderful books, and if you like suspense and can handle some pretty intense visual descriptions of dead bodies, then definitely give these books a read. Trust me, you’ll be glad you did. The first in the series is Relic. You should probably read this first, as it introduces Agent Pendergast and several key players in later books.
