Did you read A Discovery of Witches by Deborah Harkness? Fun and a great vampire/witch plot line! It is an adult book, but still very fun and a quick read.

I also just read A Fault in Their Stars and it is witty and funny but incredibly sad and poignant. Little Bee is another incredibly sad but poignant novel. It has great depth but provides moments of comic relief too.

For a good mystery, I really enjoyed The Body of Christopher Creed - my students enjoy this piece too. Other good YA novels that I enjoyed: The Book Thief by Mark Zusak, Twisted by Laurie Anderson, and The Hunger Games by Suzanne Collins as someone else suggested. 

Check outUglies, Pretties,andSpecialsby Westerfield. It's about a dystopian society with a lot of fun technological toys and advancements that the young kids use to fight the controling government. All of my 14 year old students love this series!

If you have not read The Giver, I heartily recommend that book.  The themes of what constitutes a perfect society are very thought provoking.  I would also recommend James Patterson's Maximum Ride series, which is about teenagers who are two percent bird.  I would also recommend anything written by Robert Cormier who has a way of leaving you on the edge of your seat from chapter to chapter.

If you have not readThe Hunger Games, read them.

Another great author I'm personally just becoming interested in is John Green.  He writes realistic YA fiction--interesting characters and stories, unique sense of humor. 

I think that modern teenagers still enjoy The Outsiders. It speaks to a lot of themes that are still important today. As for the specific topics you mentioned, I have to agree that that Sherlock Holmes mysteries are still as entertaining as anything out there. I have heard nothing but good things about the Hunger Games series, if that's your thing, and of course, there's nothing wrong with enjoying the Twilight books either (though I haven't actually read any of them or seen the movies.)

You might want to try Anne Rice's vampire series, beginning with Interview with a Vampire.  All of the series is available in paperback and at most libraries.  There is nothing wrong with the Twilight series, but Rice is a wonderful writer, and her vampires truly come to life for the reader.  She also has a series of books about witches, I think they are called the Mayfair witches, and there is some overlap in characters between the two series, which is always fun. 

I thought your question was so challenging and appropriate for this time of year that I posted it for general discussion. You can access this by clicking on Discussion and then on New Discussions. You should be getting a lot of suggestions.

I have given the New Discussion the heading: Summer reading for 14-year-old boy?