Giant Book of Mensa Mind Challenges - Exclusive club for the smartest 2% of the population

Here is my personal back story on this little gem. I had never heard of Mensa until a few years ago, when my girlfriend and I had a competition. To see who is the smartest. So she brings out this book and we plow through a few of the challenges, until my brain hurts from too much thinking. That is when I find out that "Mensa" is the smartest 2% of the general population. There are a few online challenges as well. Are you a two percenter? :-)