So if we look to the first season on the anime--which, at this point, I reckon most readers will have seen before backtracking to the light novels--it had this odd split. The first half of the series takes place in Sword Art Online. The second half in Alfheim. So this volume covers the first half of the Alfheim arc. In anime form, it's not my favorite part of SAO. It's fine enough, but doesn't have the same energy or charge as the opening arc. This problem doesn't feel quite as marked in light novel form.
And if you've seen the anime, you know what you're getting here: Starting a few months after Kirito awakened from his time in SAO, he's fallen into a routine. It's a routine of waiting. In the aftermath of beating SAO, almost all the surviving SAO players have woken up and, like Kirito, recovering. But a handful hasn't yet woken, including Asuna. So Kirito is in limbo: Back in the real world, yet unable to connect with the woman he loves. So he goes to the hospital, sleeps, casually makes jokes with his sister, and generally drifts through life. All that changes when one of his old SAO friends comes upon a screenshot taken in a new MMORPG where an imprisoned character looks a whole lot like Asuna. Needless to say, Kirito needs to get back into the full dive life.
This section flips between two main characters (with a very occasional third): Kirito (which are written in first person) and his sister (written in third person). Well, we say "sister," but she's actually a cousin, which matters because she has a bit of a crush on Kirito (something apparently less taboo in Japan). Even she knows this is a doomed crush--he has Asuna, after all, and even if they're technically not siblings, they were raised as siblings--so maybe that's why she's taken to playing Alfheim, where she's risen to be a top player in her faction. And unfortunately, it's in Alfheim where she meets Kirito at the start of his quest for Asuna, neither knowing the other is who they are, literally in the same real world house.
So there's a bittersweet sense to this whole volume. Kirito physically advancing his quest is good--we need Asuna saved, damnit!--but his sister becomes a charming character in her own right. We empathize with her situation, and the cruel twist that the in-game guy she's kind of falling for is also her brother. And the advantage of a light novel over the anime adaptation here is we get a lot more of her perspective, allowing it to feel like a major thrust of this arc, rather than some side drama. As satisfying as some of Kirito's battles are, it's this tension between two siblings (er, cousinlings?) playing together without knowing who they are that makes reading this volume so damned addictive.
Anyway, if you weren't so fond of this arc in the anime and were iffy on whether to read on after the SAO arc, I can say--as someone who also wasn't so fond of this arc in the anime--that this is a good read. I can't guarantee anyone else will agree with me, but the strengths of the arc are much more apparent in written form.