My understanding of ADOM, which could be wrong, is that it has a lot of problems where you either know the right answer going in, or you don't. Like, problems where once you learn the solution, they aren't problems anymore for your future characters.
It's a very feature-rich game. There a lot of ways you can get screwed, but also a lot of potential options to exploit. I think it would appeal more to Nethack fans than Angband or Crawl fans.