That's what's just happened with the new book, and it's okay. It's part of the process. As usual, I've been finding my way into my character's world, and most of what I've set down is backstory and scene-setting that doesn't really advance the plot. I may use some of it elsewhere; the rest is useful mulch. Stuff I need to know to tell the story, even if it isn't in the narrative. It happened with The Quiet War - I was 30,000 words in that time. Too much background; too much hesitation before plunging in. It didn't happen with Gardens of the Sun because it picked up The Quiet War's story, and I knew enough about the fictional framework to work out exactly where I needed to start up again. All good. But then I had the same problem with one story strand of In The Mouth Of The Whale, and I didn't get that fixed until I realised that the character was a librarian, not a cop. A small change that made all the difference.
I was diverted from the new novel, in fact, because I had to deal with some useful comments my agent made about In The Mouth Of The Whale. Fixed those, sent the MSS back to my agent, who's about to send it off to my editor. Went back to the new book, saw it wasn't right, and inside a day had rebooted with a new beginning. Starting where the narrative really starts, as far as the character is concerned. And now that he's in a lot more trouble than he was before, I feel a lot better.