Sword Art Online, for those who haven't heard of it, is a novel/anime/manga series in which the players are trapped in a videogame where if your character dies, you die in real life and they have to win the game to escape. The original story was told in one novel, which I always felt was a bit too short....
SAO :Progressive is a alternate take on the story, retelling it in expanded form and filling in gaps in the original story. The series focuses on Kirito, a beta tester for the game and determined to survive and level up, and Asuna, a relative 'noob' but possessed of great determination and natural talent.
What I think SAO Progressive is very good at is being s nice blend of serious and comedy. YES there's the life and death crisis, but the books manage a lot of humor. Poor Kirito is HORRIBLY bad at figuring out women in general, which makes for a lot of comedy in his interactions with Asuna and the information broker Argo.