Thank God people are moving towards this modality. I have a fervent hatred for textbooks and publishers. The former are antiquated, static, badly formatted, and often ride with distracting garbage in the margin, or worse inline. It makes actually reading them far more difficult than needs be, with unremarkable asides that may span pages and that are easy to get pulled into. While I understand that they have a purpose, they aren't for everyone so having a platform with the dynamism of a webpage is something that I hope will inevitably lend itself to future development along this course. Not to mention being able to have interactive questions that give quick feedback rather than requiring turning through pages to find out if you're on the right track... And this interactive stuff is just an excellent means to drive meaning from terse and difficult to explain systems.<p>Cheers to the folks that put this together, a thousand thanks for the travails you've been through to blaze these trails!