Hacker News Reader

The posted link leads to an article about typography. Your link leads to an add of some book.

It's an online free-to-read, donation-supported book on typography. He just linked to the wrong page.

Which is described in the page he linked, by the way.

Index page link:

Edit: HN is graylisted by the site, presumably due to large numbers of non-paying referrals.

Your link leads to the same adpage.

Copy and paste the link in to a new browser window and then you will be able to read the book.