Despite its setting, I prefer to not see it as an MMORPG fantasy series. It doesn't contain much in-game activities usually seen in novels of that genre. It's not really about adventure, but more of a "building a new place for us to live in" type of story.
I loved reading LMS, so I can't help comparing the 2. LMS focuses on adventure; fighting mobs and boss monsters, gathering loot, completing quests and exploration etc. which gives you the feeling of actually playing an RPG game. To me it's fun because it's very familiar. I played alot of MMORPGs in the past.
In contrast to that, Log Horizon is something very different. It still has MMORPG style incorporated within it but it doesn't end in that. The story centers on the Catastrophe (the event where all the players online at the time were "sucked in" into the game) and how the players cope, live and interact with their new "reality" that they're stuck in after that.
So instead of adventuring, questing, boss hunting, loot-gathering etc. The story focuses on figuring out how they can interact with their "new" world, how much impact their presence have on it and vice-versa, finding their identity and culture, building a new place for them to live in and finally pushing the boundaries of possibilities limited by the in-game mechanics that is set in it. It kind of touches on the post-apocalyptic genre with regards to this but instead of the usual "gloomy acceptance" mood, Log Horizon has a more hopeful "Let's start from scratch" mood which is kind of refreshing and nice.
While it lacks the thrill of adventure, it gives a more satisfying feeling because the characters in the story is trying to achieve a higher goal than just self-imrprovement such as leveling and completing quests. A boss fight in other titles might give you more exitement but personally it pales in comparison to how it feels to read about characters working together in building something epic from nothing, which is what this novel is all about.
So you might get disappointed if you find out that it's not really the usual VRMMORPG type of story that you're looking for, but don't focus on what it isn't and focus on what it actually is; a very solid story that is full of depth, hopeful and promising. It's still ongoing and by the looks of it, it hasn't even reached half of its potential depth yet.
P.S.
If you do decide to try it, don't give up on it until you've read vol. 2. That's where all the fun starts ;p