At the risk of unpopularity, I will admit that I was not a huge fan of Matched. It was okay, but my expectations were Hunger Games high, and the book didn't meet them. There was very little tension about the eventual choice that Cassia would make, and yet I really didn't understand her decision.
That said, I thought Crossed was a far stronger novel. In it, Cassia has determined to risk everything in order to find Ky. The story is told in chapters alternating between their two viewpoints, and Crossed is far more action-packed and fast-paced than Matched was. Cassia and Ky are both challenged in ways they have not been previously, and we learn more of who they are as they rise (or fail to rise) to these challenges. Several of the characters from the first novel are off-stage in this one, but new characters are introduced. Unlikely alliances are made. Stakes are raised. Cassia and Ky are growing up fast, and their relationship is both maturing and tested in this book. And while this volume focuses primarily on Cassia and Ky, don't write off Xander. He is still very much a part of the story. I expect we'll see a lot more of him soon.
I was somewhat ambivalent about continuing on to this second book, but I am now looking forward to the conclusion of this trilogy. Condie has done a good job setting up the endgame. With luck, the third will be the best yet.