Being from the East Coast the Hoover Dam wasn't exactly on my sightseeing radar. I vaguely remember learning about it but nothing much stuck. Hubs on the other hand being a NorCal native had always wanted to go...so we went. Hoover Dam is a very worthwhile tourist destination if you're in the neighboring Nevada/Arizona area. I learned A LOT and glad I went.
The experience starts with a short movie overview of the building of the Dam and then you can do the Power Plant tour ($15) or the full Hoover Dam tour ($30) which included the Power Plant. There are plenty of opportunities to take pictures and the tour guides are very knowledgeable. We did the full tour and it takes about an hour. You're walking through tunnels that are very deep underground so it's not air conditioned.
The only thing I'd recommend is that you bring your own water and/or snacks. The snacks and such at the gift shop are quite expensive and once you're on the tour there's nowhere to get anything. Also, wear comfy shoes and light weight clothing.