Zombies, so lots of violence and gore, some implied sexual references. No holds barred on the language, either. Probably teen-appropriate (depending on the teen). If you’d let them watch the TV show, there’s gonna be nothing new here.
Doesn’t require any previous comic knowledge; standalone continuity. The comic informs the TV show but they are two separate continuities; however, if you like one, you’ll probably like the other.
I really enjoyed the Walking Dead the first time I read them, but re-reading them as been (for some reason) very tedious. Maybe it’s burnout on the zombie genre, which wasn’t really in full swing when these started to come out. Nevertheless, if you like zombies, it’s worth a read.