It was kind of aimed at teens and twentysomethings, but I watched it in my early thirties and liked it. There's a spin-off novel now too.
I have never watched it. The name put me off. Until I just looked it up right now, the title gave me the impression that it was some kind of bitchy drama with Desperate Housewife like characters. Veronica Mars sounds like the name of a female escort, drag queen, or fashion model, not a teenage crime vigilante. If she had a different name I might have paid it more attention.