I would select elementary physics book. For me the development in physics is worth more than knowing the history or past stock movements.
If I know the future, I can make a ton of money. The other suggestions I've seen are good, but mostly just satisfy curiosity about distant future events. I would rather make an obscene amount of money and work on current day problems or curiosities.
I would love to have the tech, but I fear anything useful would either be too hard to understand or too big.