I've run three Paizo APs, Reign of Winter, Carrion Crown, and Iron Gods. Reign ended with TPK in book 3, Carrion ended in book 2 when covid shut down my face to face game, and Iron Gods ended in finishing book 3 when a RL medical issue came up.
All were excellent experiences to run for me with good games but some frustrations. All gave great opportunities to riff on their fantastic themes and throw in additional similar material.
The Paizo AP forums gave great advice and were good resources I used in running all three.
Carrion Crown is the earliest published and has the least foreshadowing of later stuff but the forums had great advice for introducing the book 6 BBEG in the first book 1 scene and connecting him in for others that I used to good effect. I really dig D&D gothic horror and so was enthused about the AP theme. CC is also fantastic if you want to climax at book 3 and turn that chapter BBEG into the true AP BBEG. Legendary Games has two great supplementary lower level modules I used that fit in well. Chapter 4 is Lovecraft themed instead of classic gothic horror themed and I like it but it can throw off the vibe for some. I dig it though and was considering expanding with the Carrion Hill module as well. Book 5 on vampires read kind eh for me, and six which is lich themed is probably the least gothic horror of them all and the most high level D&D magic and undead.
Reign of Winter was great through books 1-3 which I ran. The witch sleep hex is super strong though as there are a lot of low will big bruiser trolls and giants and beasts and such. I ended up banning it once I saw its effects on my game in this AP. Book 4 was a bit weird, I was considering swapping in something else for it, but 5 looked amazing. Six did not quite stick the epic landing from my read.
Iron Gods has been amazing, Thundar the Barbarian theme with Mad Max and Mage the Ascension Technocracy. Not always the easiest to find the information I wanted while running it though (the names of the individual lords of rust is kind of buried in a not obvious place when looking for them for example).