Thx for plug. Indeed it would be a good book for any highschooler interested in more advanced topics.
> I'm surprised it's expensive now.
Yeah amazon pricing is weird. My intent is for the book to be sold ~$30, but if I tell this price to amazon they start selling it for $20 after discounting, and then readers buy it less because they think it is not a complete book, but just some sort of summary notes. Nowadays I set the price to $40 so that after amazon discount the price will end up around $30, but today it is expensive indeed... I might have to bump it down to $35 at some point.
It's very possible if you purchased it when I had set the price to ~$30 and amazon was discounting it to ~$20.
BTW, I've released several "point" updates and the book is now at v5.3. Please reach out by email if you're interested in having the PDF (I have a free-PDF-with-proof-of-purchase-of-print-version policy, including all updates).
> I'm surprised it's expensive now.
Yeah amazon pricing is weird. My intent is for the book to be sold ~$30, but if I tell this price to amazon they start selling it for $20 after discounting, and then readers buy it less because they think it is not a complete book, but just some sort of summary notes. Nowadays I set the price to $40 so that after amazon discount the price will end up around $30, but today it is expensive indeed... I might have to bump it down to $35 at some point.