Twilight is the biggest YA book since, well, since ever. Stephenie Meyer's romance/horror juggernaut tells the story of Bella Swan who moves from Phoenix to Forks, Washington and meets the mysterious Edward Cullen. Edward is unlike any other boy she's ever met.
He is super fast, glistens in the sun, can stop speeding cars with his bare hands, oh, and has been a vampire since 1901.
Twilight isn't the best book I've ever read. It's full of gushy romantic cliches, is probably about 100 pages too long and will probably date very quickly. That said, it's still basically a good story. Meyer has a very fresh approach to the vampire genre. The Cullen family are 'vampire vegetarians'; they don't hunt humans, they hunt animals. The family does try to fit in as much as they can with the humans and even help them out. And no, they don't sleep in coffins.
It is a good, light read, something to suck you in this summer. (bad pun, I know...)