This is definitely offputting:

> If you're unhappy with the price, then please feel free to take 6 years to learn, test out, write-up and maintain everything contained in the 100+ pages of my new eBook.

Or maybe I'll just buy a cheaper book from someone else?

Hmm not a bad idea. or may somebody could just maybe you know, pay the $100, rehash it and sell the summary/rehash of the book for $20? Even different translations of it.

On a more general note, I wonder if a group effort/initiative exists to "open source" the rewrite of contents of these unbeleivably expensive text books? While content can be copyrighted, the re-explained content versions of these cannot be right?

Yep that line would make me not buy this. I don’t care for that kind of sneering language.

I think a fair benchmark is https://haskellbook.com/.

It's $60 and the absolute most I'll consider and have spent on a book of this nature, outside of botique ancient stuff....and is really well written as well as has a pretty ambitious goal (teach Haskell and programming more generally from the ground up).

I think that’s a fair benchmark, too. It’s a well-written book that starts from first principles — something I don’t see often in books. While I don’t use Haskell everyday, the things I’ve learned from that book influence how I write code every day.

It looks like 180 pages is with ePub formatting:

> The ePub has 180+ pages, the PDF has 100 A4 pages.

Depends on how good it is ultimately. I've read a _lot_ of programming books. Some were obvious, some were good, and some elevated me in a way I am unsure I would have achieved on my own. Given the tremendous salary opportunities in the field, its tough for a book price to be too high, if its good. And sometimes, reading a few bad ones is the only way to find the good ones.