I have always found the historical part of the Hoover Dam intresting. The video they show before the tour stinks. Honestly, the tour guides stink as well.
No matter, you can get alot out of it just walking on top and walking around it. The tour information is simple stuff that's listed on wikipedia or it's site anyways.
I enjoyed the design and engineering aspect of it. Prices, not so much. Parking is like $7 and the sub-par tour is $11 each. Don't pay for the $30 tour because they just take you further into the dam but the same substance of information.
Tip: Much better to see when they first open. Less crowds. This place is swarmed with people and makes Route 93 sooooooo slow. If you come at night they do not permit foot traffic, but the pictures are much better at the observation points if you have a decent camera with good night qualities/selections.