It says so in the email I just received.

From: Simon St. Laurent <oreilly@post.oreilly.com>
Date: Wed,  6 Jan 2016 03:06:03 -0800
Subject: Free ebook: why static sites are the next big thing

Hi Marco,

Given the choice between static and dynamic websites, why wouldn't you choose
to serve custom, dynamically generated content to each visitor to your site?
Yet to the surprise of many, static websites are coming back. Having been
ridiculed for years, they now fulfill a vital need for bloggers and others
who simply want to disseminate information.

Static site generators — the new breed of tools for creating static sites — 
simplify the once-tedious process of building and deploying these basic sites.
Get the lowdown on these tools and see what's behind the return of the static
site with Static Site Generators, a new report by Brian Rinaldi.

Get the free copy.

Simon St. Laurent
Strategic Content Director

Right when I’m getting serious with Jekyll. There, skipped HTML 2 through 5 but now I’m back ahead of the pack. For completeness: the free copy referred to can be got here.