This is the first part of a two-parter, and it's definitely a fun change of pace! I will try to keep this relatively spoiler-free, but players should probably just know that we really enjoyed this module and it's not all fighting.
What I liked
Unlike most AL modules, this primarily will test the characters (and players) ability to handle social situations as well as explore their environment to carry out infiltration and espionage assignments. It does this pretty well for the most part, including some pretty memorable scene setting. The fact that the adventure includes - and in fact needs - no maps whatsoever helps with this, because we can run it in "theater of the mind".
In almost all situations, the adventure has a fairly open design, encouraging the DM to reward the players' creativity and come up with their own solutions. This will keep everyone on their toes as the adventure proceeds, but that also means everyone works together to create and tell a cohesive, interesting story. Related to this: the adventure has explicit failure conditions! The players can do what they like, but if they make poor choices, they could find themselves on the outs with little to nothing as a reward other than the fun of play itself.
The module does include some combat, and the final fight provided a lot of entertainment. A few "WTF!" moments from the players really cemented that for me - it was a well-balanced fight for five characters between levels 2 and 4. (Hint: clerics and paladins can really shine!)
What I didn't like
Despite the openness, the adventure starts off with a pointless "roll to continue" mechanic. What happens if the players fail the investigation roll? That would be boring and the game session would last less than five minutes. Bleh. Also, the use of spell scrolls to get them into the Tower misunderstands how that mechanic works, because any class without that spell on their list (and indeed any non-spellcasters) can't use those scrolls.
Tips and conclusion
The above are minor nitpicks. I replaced the scrolls with a frail old bard who just needed to cast one seeming. Also, the main event seems to take place at Midsummer, but the next module (Death on the Wall) keeps talking about heavy snow. You can either move this module to Midwinter or change the references in the next module to rain (I chose the latter).
This provides an epic penultimate session for the storyline and I really recommend it to groups looking for something other than "I look for traps around the door" and "I swing my sword at the monster".
[5 of 5 Stars!]