A lot of people seem to like this adventure very much.
I didn't quite as much.
For me it seemed less about horror but more about hack and slash dungeon crawl with undead.
The trust mechanic is terrible.
And I think throwing one big, powerful magic weapon at the PCs instead of letting them find several weaker ones lead to PCs sitting around during fights doing nothing because the enemies where immune to mundane weapons.

As the title states, this was by far the best of the first three parts of carrion crown.

There are many good things to be said about The Haunting of Harrowstone, as you can see in these reviews. I have just finished GMing it with my group, and I will join the choir. Sure, there are things that need tweaking - the trust point system for instance - but they are minor, to my eyes.

Depending on your group, the module can be played like a railroad or like a sandbox. You can give the players information that shoot them straight towards the mysteries, or you can let them explore the town and slowly uncover things. In my case, I have players that love a good mystery, and that actually want to bond with (or provoke, or quarrel with) the NPCs I put in front of them. And it has worked well.

The atmosphere is great, the writer created a good gothic feel to the monsters and the events. The NPCs are memorable and the hidden facts are possible to decipher without being too obvious, I think. The locations are dark and gritty, the monsters challenging and fun.

Also:

The Haunting of Harrowstone gets 5 stars from me.

An amalgamation of popular horror stories and themes in the land of things that go bump in the night may sound cheesy but so far has been excellent. It's like an RPG version of American Horror Story...everything that's ever creeped you out, even a little, is included but with brand new twists.

The vivid setting of this AP is the nightmarish country of Ustalav centuries after the fall of the Whispering Tyrant. Your group will be called for a seemingly straightforward task of attending a funeral but will quickly find yourself intrigued and repulsed by the strange happenings in the town of Ravengro. Soon your group will begin investigating a horrific mystery involving long-dead murderers and a possible link to the Whispering Way.

My favorite things about the first book of the AP:
1) Intrigue – The Gothic setting and the whispers of cult involvement piqued my interest in unraveling the plot lines.
2) Challenge – There are some genuinely dangerous encounters in the Haunting.
3) Writing– The game is supposed to be horror themed and it does not disappoint. The descriptions are well-written and add to the overall atmosphere of the game. Our GM chose to play spooky music during most games which also added to the feeling of delightful unease.
4) Originality – Many of the characters and events in this book are roughly based on popular movies and books. Still, each character manages to be unique and memorable. I didn’t feel like I was experiencing a string of copied and pasted stories with a new name tacked on.

Least favorite things:
1) Trust points – I don’t know what these are really but I’ve seen them mentioned in other reviews. If our GM used them she did it without our knowledge. We were told to have a secret in our character’s history that he or she would not share with the party right away. The secrets have added a really interesting dimension to the game.

2)A few loose ends – At one point some children in town were chanting a truly gory, disturbing song while playing jump rope. I was curious about if they were possessed or doing it intentionally and hoped to find out. After we cleared the prison we never really found out what the deal was so I assumed the kids were affected by the darkness from the prison. I think the little details like this could have been tied more neatly into the overall story.

This review is based on a playthrough with a group consisting of a druid, a rogue, a sorcerer/cleric, a magus, and a ranger (the ranger died and was replaced by a paladin) and the experiences we had playing the adventure.

<--POTENTIAL SPOILER WARNING!-->

The Carrion Crown adventure path begins with a classic ghost story, a tale of an old prison haunted by unspeakable evil. While The Haunting of Harrowstone has its issues, it's a good mix of atmosphere, story, and creepy action.

Good things first:

1) The atmosphere presented in the adventure is awesome. It's gloomy and tense from the get-go and the tension only increases as the adventure progresses and the characters realize what's going on up in the old prison.

The physical description of the prison itself added a lot to the atmosphere as well and the players really felt that this was a spooky ruin and that terrible things had happened there in years past.

2) The story, while not unique, is engaging and flavorful. The plot is revealed gradually and the big reveal, an encounter with the ghost of the warden's wife, was a pleasing way to reveal the final pieces of the puzzle to the players and set up the final encounters.

3) The research felt like a page right out of a Call of Cthulhu adventure which, to my players and me, is a good thing. Although the characters failed to learn everything there was to learn about the prison and its prisoners during their initial research in the temple's archives and the townhall library, the prison itself offered additional means of research.

4) The use of haunts worked very well in this adventure. Haunts make for excellent low-level encounters and the game mechanics mixed with the flavor inherent in any haunt makes for a fun way for the characters to learn more about the adventure's background while keeping them looking over their shoulders. For a ghost story set in a ruined prison, the haunt mechanic is perfect and the haunts presented in The Haunting of Harrowstone were very well written.

5) Artwork. Overall, the artwork in The Haunting of Harrowstone was top notch. Especially the half-pagers done by Craig Spearing were phenomenal and really helped me as the GM to set the mood.

The Bad Things:

1) Pacing. We felt that there was an issue with the pacing of the story. As the adventure is written, the characters have roughly 30 days before the evil spirits haunting the prison escape and wreak havoc upon the town of Ravengro. It took the characters 7 days to wrap up the adventure and move on to the next adventure in Ravengro. Since the major clue to what was going on, a name written in blood, was spread out to match those 30 days, we felt that the 30 days was overkill. Half the time would have worked better, we felt, and might have added a bit more urgency to the adventure.

2) Trust. I didn't use the Trust Points system at all. I felt that what the Trust Point system was meant to achieve was just as easily achieved through simple roleplaying. To me it felt like extra book-keeping, and so I didn't bother with it. The adventure worked quite well without the system.

3) Artwork. As mentioned earlier, most of the artwork in The Haunting of Harrowstone was top notch. The exception was the Bestiary section. The artwork for the critters presented in that section didn't work for me at all.

The Verdict

A very good start to the Carrion Crown adventure path. There were some minor issues but those were minor and didn't take anything away from a solid ghost story filled to the rim with atmosphere and classic horror. My players felt that their characters were challenged and I felt that I'd successfully GMed a storytelling genre that, in my mind is somewhat difficult to pull off in a game like the Pathfinder RPG, namely horror. That wouldn't have happened if I didn't have a well written adventure to work with.