It's Gloomhaven. If you are a board gamer you already know what to expect, if you are not, this is NOT the game for you to start with. Since I've previously written about Gloomhaven Jaws of the Lion (JOTL), I'll just copy my own words from that review.
Gloomhaven is a co-operative, fantasy-themed, campaign-based tactical skirmish game. Over the course of a single campaign you will play 30-50 individual scenarios each taking about 2-3 hours. Each scenario will start with an introduction that ties the scenario to the overall campaign, present you with a small map, and give you an objective to complete the map. You and your fellow players will work together against the "computer controlled" monsters.
On your turn, Instead of using dice you will have a hand of cards each allowing you to move, attack, heal, etc. When it's time for the monsters to act, you will pull an action from deck of cards unique for each monster. A great system.
The "campaign" or "legacy" aspect of the game comes from both the overarching story tying each of the scenarios together and the ability to "level up" your character by choosing from an ever expanding set of action cards that you have to choose from.
Knowing this game has just a ton of fiddly little parts I decided that some kind of organizer was essential. I decided on the Smonex Wooden Organizer. At $110 it was not the least expensive option but it does look very nice. On the downside to say that "some assembly was required" is a major understatement. It comes flat packed and is assembled like a giant puzzle. I figure it took me 5-7 hours to put all of the pieces together.
  
Tim:
3.9/5 Good
I've written and re-written this a few times, but to many versions have been felt more like rants, so one last try. At this point we have "finished" the main "Kill the Big Bad" scenario and are just going to call it done.
First, If the idea of a co-operative, tactical fantasy game with a legacy component appeals to you, get and play Jaws of the Lion. To my view it's just the all-around better game. Tighter and more focused, cheaper, easier to setup, and it can be completed in 20-25 hours of play.
As for Gloomhaven. The central mechanic of cards for actions and stamina is simply brilliant and if you like it you will get enjoyment from the game. It is very fiddly and many of the scenarios seem to double down on the fiddlyness but I would put that more under "things I wish they would tweak" rather than major unfixable issues. My only real complaint about the combat is the high level of randomness which seems out of place for a tactical combat game.
But then the issues start. I'll group them loosely into "cooperation" and "randomness".
Is this a co-operative game or not?
The standard reply seems to go along the lines of "players are incentivized to make suboptimal plays in the interest of making their character stronger later. Each player has to decide how selfish they want to be, and whether that selfishness will ruin the group." to which again I ask the question, "is this a co-operative game or not?"
Randomness
Yes it's amazing they developed a game that more like an open world video game than a board game. But as with all things, tradeoffs have to happen. In this case the tradeoffs make luck more important.
So I understand the intent was to make an open world game with lots of randomness. What I got from all of this was a mess of ideas. Great ideas, but they ended up feeling just arbitrary and random.
Laura:
3
I had such high hopes after enjoying Gloomhaven: Jaws of the Lion. I expected the original Gloomhaven to be just a longer game with more interesting branches. While that is true, they also included some mechanics that made the game not as fun - and didn't highlight that they were important for other aspects of the game. Why do I need to retire a character after a secret battle goal has been met? Why do I have to give to some clan/order/group just to get better items in the shop, or to upgrade my character's ability cards? Why am I randomly punished for road or city events? Why do some scenarios also require players to increase the amount of curse cards in their personal decks? Can the game creators just be sure the scenario is balanced without relying on these cards lurking in the personal modifier decks, waiting just to make sure a plan not only fails for the round, but possibly the scenario? I know not every scenario should be winnable at the first attempt, but this seems like a poor way to fail.
With that said, it was a good game that had many skin-of-your-teeth wins, with scenarios that required changing tactics halfway through in an effort to win. Those were highlights, being able to work together and change play style and take risks in hopes of winning. While I overall enjoyed the game, I don't think I would have stuck through it had I not played and thoroughly enjoyed Jaws of the Lion. I am interested in playing Frosthaven, but possibly not until 2025!
Gloomhaven's run of five years and two months makes it the longest-reigning BGG number one to date