I agree with pretty much everything Knick says above. I don't think there's a compelling need to meet Eodred's Korvosa, but you do need to make sure the PCs are rooted in the city before they set out to save it.
My experience with Book 3 was identical -- there's all sorts of good stuff in there, but as written, it's a mess. The DM is left doing a lot of spadework, and the Arkonas' palace in particular can be lethal if the DM is playing with gloves off.
(Book 2, let's note, is pretty close to perfect. Up until then, it was hands down the single best module Paizo had produced, and it's probably still in the top five. It requires very little effort to make this a creepy, challenging, and truly memorable experience.)
Book 4, Knick nails it -- it's a fantastic sourcebook for the Shoanti and the Cinderlands. As an adventure, it's a kind of annoying railroad where you march from quest to quest collecting plot tickets. There are some cool bits -- the initiation ritual, the Havero, aving to jump into a giant worm's throat at the end. But a lot of PCs will chafe at the unfortunately obvious railroadiness of it all.
Many, many people have already pointed out that Cinnabar is an NPC with a cool backstory that eats up a page of text and *impacts the plot in no way whatsoever*. Something should be done about that. Have her show up earlier on, at least. Also, spend more time with the Shoanti, because the Shoanti are interesting.
This was my experience exactly - Book 3, the Arkona mansion would have been a TPK in Pathfinder if my PCs had fought them, although luckily they had no reason to do so and it was clear from Vimanda that facing Glorio would be suicide.Book 4 is a terrible railroad, my campaign avoided it entirely since IMC the PCs made friends with the Brotherhood of Bones in bk 3, and thus found out Serithtiel's location from them, avoiding the whole Shoanti fandango. Which was ok but made Bk 3 a waste of money, it boiled down to a single lopsided fight where the PCs ambushed pursuing party of Cinnabar/Cinderlander/Gray Maidens, in turn ambushed by a Red Mantis & gargoyles, but cleaning them all out pretty handily.
I think if CotCT is rereleased, Bk 3 needs editing, Bk 4 needs to be changed completely, much more open, and with much stronger hooks, eg the Shoanti could be gathering to sack Harse.