You can’t get moe up to date than The Millennium Problems: The Seven Greatest Unsolved Mathematical Puzzles of Our Time, by Keith J. Devlin, an introduction to the seven pullzes whose solutions will earn a $1,000,000 prize.

The books of Ivars Peterson are a good popular introduction to most areas of math. The Mathematical Tourist is subtitled “Snapshots of Modern Mathematics” and has a 2001 revision. He has a series of others out.

*Mathematics Today*, edited by Lynn Arthur Steen, is a series of essays on various branches of math but it’s from 1980 and out of print.

You could also try one of the huge number of books that have come out in recent years on problems like Fermat’s Last Theorem, the Reimann Hypothesis and Goldbach’s Conjecture, because solving those gets you into an enormously varied amount of math, and it obviously must be presented in a way that ties them all together.