So the best book you read this century is about an event from early last century?
Can't tell mine, only now that I got a smartphone I got into literature again -- free time on the bus -- and I began my search for the lost time with classics centuries past. The only two books from this century I've read are both available online as free downloads:
After Life, by Simon Funk quite average amateurish writing, but bearing awesomely vivid imagination. Mind boggles and I recommend it.
Accelerando, by Charlie Stross Barroque hi-octane language full of tech jargon. Still to finish it, but a recommended read.
both about the rise of a supposed technological singularity.