Ok so I've never listened to Iron Maiden, is Number Of The Beast a good starting point?
Short answer: Yes, BUT...
Here's the thing: It is a landmark album. But it is a product of its time. And that may understandably keep it from clicking for you. It's a good listen. But it isn't even close to their best. Way back when DT were first planning on covering an entire Maiden album, their thought process was along the lines of [and I'm paraphrasing what they have said]: "We felt like Piece of Mind was a stronger album, and we liked it better. But Number of the Beast is such a classic that we felt that, if we were going to cover an entire Maiden album, we had to go that route instead."
And here's another big piece of the puzzle that I would include when considering modern Maiden: They are the quintessential LIVE band. Their live performances are second to none. Seriously. There are only a small handful of bands where, if a fan asked me what to listen to to sample the band, I would recommend a live album instead of a studio album. So if you want to check Maiden out and see if they are for you, I would recommend sitting down and watching either of these: (1) Rock In Rio, or (2) En Vivo! You can find both complete shows on YouTube in HD with good sound. Honestly, either one of them will do. I was skeptical of En Vivo!, but a former forum member said it was perhaps THE definitive Maiden live show, and after challenging that view, I watched it and agreed with him. I think it is the stronger of the two. But most people you ask would probably go with Rock in Rio. But you can't go wrong either way. If you check out one or both of those and you still don't really care for Iron Maiden, I think it is very safe to say that they just aren't for you. But if you are open to what they do, those will totally hook you.