I'm just over halfway through and a little disappointed with it if I'm honest - it suffers from too little honing as did a couple of the later HP books...chapters where very little happens at all and it all gets quite boring & very put-downable.
As a reader you know you're being fed the occasional clue but so great are the gaps between them all that it's a separate activity to put them together; so I just ignore them, which then really makes the long parts where-not-much-happens quite pointless.
As a writer myself, I know she can accomplish the same in fewer pages, with greater tension so it doesn't feel like you're wading through mud to get to the good bits. She wouldn't actually have to reduce the text by much at all.
It's a real shame since part of JKR's genius lies in how un-put-downable how writing can be and the joy of a large book is tempered knowing it would be more enjoyable for being a couple of chapters shorter.
It's difficult at times when writing to notice when the pacing is off because you're so immersed in the story and you know what it is you're aiming to achieve, but levelling the challenge to cut at your stories as you hone them is crucial.
I haven't read all this thread yet as I'm wary of spoilers creeping in but it's great to see Robin & strike being honest with themselves about their feelings for each other and I agree with the comment that they're not wholly likeable. I love that about them though, none of us are wholly likeable and I love that Jo doesn't spare them in her writing.