By a high school freshman...
It's dark and a bit gruesome, but most of these reviews are huge overreactions unless they're written by third graders. Honestly, the teens of this generation have read and seen much worse. This is what Poe's work is. It's classic literature; it inspired the horror genre that we know today. Frankly, I think nearly all seventh graders could handle this. My parents are strict about the content I'm exposed to, and I took the somewhat gory content in stride. This will do no damage to the sanity or sleep of most any (moderately mature) thirteen-year-old.
As for the actual work... it's old-fashioned in wording (read: difficult for the average middle schooler to understand) and, yes, includes death and murder. It can be a bit monotonous, especially if you're turned off by the 19th-century language.
Read it. Even if you dislike (or hate) it, you've experienced some classic literature, which truthfully could do tons of good for the average high schooler.