* Always have the call to action repeated at the bottom of the page; you did a great job having it above the fold, but I got to the end and had to scroll back up to express intent. That's a flowbreaking design.

* This is purely stylistic, but I strongly prefer the first letter of each line to be capitalized. I find the stylistic inconsistency around capitalization offputting.

* You have pretty nicely made docs, consider making the link to view the sample chapters a clickable picture of the first diagram-page in your chapter.

Thanks for making this!