Here's number Five:
Matched, by Ally Condie
Why did I love this? So many reasons -- including an actually well-done love triangle (where the world-building fully supports the tension there), great world-building (and world-unfolding -- I love how each chapter offers a new glimpse into all the tension beneath the surface), very sympathetic characters (from Cassia, Xander, and Ky to Cassia's family and Ky's parents), wonderful pacing and tension -- and although room is clearly left for the next book in the series, this story had a satisfying ending (to me) and felt complete.
The story: Cassia is Matched to her best friend, an almost unheard-of event in their society (where most girls are matched with boys they've never seen before) -- but even more unusual, Cassia is given two matches, and she knows the other one, as well. He's an Aberration, which means he wasn't supposed to be in the Match pool, but now that Cassia knows, she can't help but be curious...and soon she and Ky are developing a friendship which seems to threaten their Society in ways Cassia can't even imagine.
I'd recommend this book to everyone (ha) -- in fact, my MIL's boyfriend's daughter (who's in her early 30s) came to stay with us for a few days over the holiday, and she read it (and loved it).