Something I want to write before I forget it:
In the Sequences there are many links to books. Some of those links go to Amazon, some of them go to Google Books. Please make sure the book links in the e-book have the MIRI referral code.
This should be quite easy to check: Just make a script that selects all Amazon or Google Books hyperlinks from the book source.
Also add this to the list of things the proofreaders should check for.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.