Sword Art Online Re:Aincrad, Vol. 1 (manga) — Reki Kawahara

This might be a game, but it's not something you play.Die in the game, and you die in real life. This is Sword Art Online, the latest VRMMORPG, and upon the game's launch, ten thousand players realize they're trapped in this virtual world with no escape…unless they can make their way through Aincrad, a massive floating castle with dangers lurking on each of its one hundred floors. Enter Kirito, a swordsman and former beta tester for the game who has the knowledge and skills to rise to the top, and the rapier-wielding Asuna, whose fated meeting with Kirito will change their lives forever. Join these two warriors on their journey to freedom in this expanded retelling of the original Aincrad arc!