I would have been scared whit-less if I had read those stories as a pre-teen, but spooky stories have always fascinated my children. I guess they are secure and feel protected enough in real life to really enjoy a creepy story.
Sherlock Holmes has a side-benefit: the puzzles he must figure out are reinforcements of logical principles we work through each week as I take the kids through a logic and critical thinking text book by David Kelley. Oh, and also now my daughter is really interested in psychology as well and spent her leisure time this week reading an undergraduate psychology text we checked out from the library and a clinical psychology book that has a added bonus of reinforcing her statistical analysis skills.
Hooray for homeschooling and allowing your kids to follow their interests!