I got a chance to play. Pretty interesting but kind of confusing. I'll give a rundown of how it works for people who haven't played yet.
Basically you get a quest with a main objective and a few side objectives. The objectives are mostly about travelling to locations and spending "proofs." You can investigate while in towns, drawing a card from one of three decks (blue, purple, red) and doing whatever it said. This usually gets you leads corresponding to the color. Somehow these leads are converted into proofs but I don't know. 5 leads = 1 proof? I dunno.
Different things you do affect the war track, which is basically a wheel that ticks around. Failing tasks, drawing certain cards, or finishing a turn without any kind of obstacle to resolve (no free rides, buddy!) advance the war track and deposit monsters and Foul Fates, cards with various undesirable effects, around the map.
Fights and other tests are done with fancy symbol dice, with stuff like swords and shields and other effects on them. You have to get X swords and X shields to win completely, with consequences if you don't. Failing the attack can see the monster staying around or moving to new locations, while failing the defense usually gets you wounds or foul fates. Wounds are placed on the various actions you can take and disable that action until you heal (so if you get a wound and place it on your travel button you can no longer travel until you heal) and foul fates fore you to take a foul fate before you can use that action.
In addition to investigating you can develop, which gives you a choice of two development cards. These depend on the character, spells for Triss, friends for Dandelion, and I dunno, swords or potions or some shit for Geralt, and they're basically delaying your quests to improve your character. When you start out monsters are pretty dangerous and you'll fail a lot of tests, but developments help. As an example, Dandelion's friends, because I picked Dandelion. You can spend a gold token to place a something else token on a friend card. Then in a fight or something you can spend a something else token in exchange for extra swords or shields or other kinds of effects.
Overall it's reasonably fun. Coolio was right, it does feel like a single-player game at times. There's not a whole lot of inter-player interaction so it's mostly just doing your thing and then waiting for the other player to do his thing. It'd probably be better face to face (this is a conversion of an actual board game, after all) or with a full set of friends. With strangers it's basically two to four people taking turns playing solitaire.
Speaking of which I think this would make a pretty fun solitaire game. The multiplayer components are vestigial at best right now, I might see if you can't just start up a private room without any other players.
Oh, and each character also has a special action. Dandelion can sing for money, and Triss and Geralt use their special actions to prepare their development cards for use, Dandelion's development cards being prepared with money, as I mentioned before. Yarpen's is command and has something to do with the dorfs he leads.