[thurn]

Kind of surprised that this book could be published by O'Reilly and also freely available online? Seems unusually generous.

[darthrupert]

Possibly a sign of confidence. After browsing this for a few minutes, I'm very convinced of its quality and will probably buy it.

Wouldn't have happened with a book with just sample pages.

[jjallen]

Why buy it if it’s completely free which is implied by your post?