As a couple of folk have said, it's been running since the dawn of (TV) time in the States, where people have won huge sums.
It was also the source of a major scandal, and a feature film about that problem. And yes it has that odd feature of answering with a question, but you can get used to that.
We've watched masses of quizzes over the years, serious and more light-hearted ones, and of course not all are to everyone's taste. Stephen Fry is a very gifted chap, but he looked uncomfortable to us in that role, and kept saying "response" instead of "answer" which looked like he was just trying to sound extra clever?
In this one you can get some tough questions, as well as the easier variety, that style of having a set of questions on the same theme means that you might meet a topic you know nothing about?!
Straying to another quiz, does anyone see University Challenge? The new host (post Paxman) is Amol Rajan, has the wildly irritating habit (to us) of speeding up in the last few minutes, trying to squeeze in extra questions, so he ends up gabbling like one of those madcap American livestock auctioneers, almost totally unintelligible?!