To those who have a high IQ

You should ask this question on Reddit or a Rick and Morty forum, not here.

what is it like? Can you pick up any book, read it, and understand the gist with minimal repetition?

Instead of asking people who delude themselves into believing that they have high intelligence, you could look at correlations with high intelligence. Reasoning seems to be most highly correlated. Things like vocabulary and memory (and even reaction time) are also correlated, but to a lesser extent. I can point you to a journal article by a noted researcher if you are interested.

What is something you are able to do that you know is because of your intelligence -- the proverbial 1,000 pound deadlift of the brain, if you will.

While noting that I in no way assert that I am 'smart', the only thing that gives me that impression is the stupidity of other people. And not the stupidity of holding 'bad opinions', but not noticing large inconsistencies in their own thinking or what they are told. Or not being able to figure out the simplest things. Left to my own devices, I feel neither stupid nor smart, but just ordinary.