Quantum Computing since Democritus in high school reading list is very heavy. I have had Theory of Computation class in college and I can't read 20 pages of that book.
On the other hand, if you treat each page, each statement as something you have to completely internalize before moving onto the next page—including looking up all the prerequisite topics recursively on Wikipedia or in other texts—you might just end up teaching yourself up to college-level math while still in high school.
(I didn't do this myself with QCD, but I very nearly did it with SICP in middle school.)
To provide a second opinion: for me it was probably one of the best books I read last year -- extremely lucid writing and very lively. I think I would have loved it in high school.
QC since Democritus is a weird mix of textbook and popularization; I think you could absolutely read it without understanding the details and still enjoy it. You won't get as much, but you'll still get something.
I didn't understand much of algorithms or quantum computing when I first read the lecture notes the book is sourced from [1]. Was still worth it.
I'm reading QCsD right now and loving it. But in high school? That sounds crazy. It'd help a lot to already understand Godel's proof, big-O notation, and P-vs-NP. Also relativity and quantum mechanics. And maybe some group theory.
I'm a current HS senior who took a Theory of Computation class the year prior, and I got a few chapters into QCSD before realizing that I needed to learn some more about complexity theory before I read that book. I'm planning on trying again once the summer begins.
Now I'm about half-way through Godel, Esher, Bach, and I have to say that GEB and QCSD feel similar, with an overlap not only in theme but also in genre and style.
...I got a few chapters into QCSD before realizing that I needed to learn some more about complexity theory before I read that book. I'm planning on trying again once the summer begins.
It might be a bit overkill, but if you go over the main chapters of Arora and Barak you should have more than enough background in complexity theory for your purposes.