Book 4 was a good read, but spent way too much time on the flashback section as none of that back story stuff was essential enough to need that many pages.
The Wolves bit was similarly way too long. No need to spend so much time in that village when it was inconsequential to the main plot. What the wolves were protecting/using captives for was important I suppose, but way too many pages in that book before they get to that.
I hated how King wrote himself into the story, and in general didn't care much about all the fan service with characters from other books popping up etc.
At the end of the day the whole series is really a fan service for die hard King fans IMO, and I've never been big on him so it just wasn't my cup of tea. The core store is solid, but too long a read because of all the meandering and largely pointless stuff outlined above IMO.