Self-guided math workbook for a clever 8yo? (Honeschool-types particularly invited)

So my kid is pretty good at and and quite enjoys doing math. Her school math classes are pretty boring for her. She likes when I talk math with her and give her harder problems than she's "supposed to" be able to do, and when I toss odd topics at her like imaginary numbers. That's fun, and I'm not going to stop doing that.

But I'm thinking that it could also be good to get some kind of a more-advanced workbook to give her that she could poke around in on her own, and maybe come to me with questions as needed. I'm sure such a thing exists, but I don't know how best to go about finding it. So, suggestions? The more specific, the better.


Self-guided math workbook for a clever 8yo? (Honeschool-types particularly invited)