I've read The Secret History a few times and absolutely loved it. The Little Friend is another story. It's actually put me so far off her stuff, I've been avoiding The Goldfinch. If you're 80% way through and do want to know more about how the Robin mystery pans out, definitely keep going. It would be difficult to say it really improves very much from here, but from memory, the pace does seem a little faster. Good luck.