A couple of practices or methods that are very relevant to blended learning that aren't included in this book that Horn wrote with Heather Staker are:
1:1 or one to one, and BYOD (bring your own device)
Terms mentioned only briefly:
OER Open Education Resouces (mentioned once in passing)
LMS or learning management system (again once in passing) How can you even think about blended learning without considering a learning management system.
Also missing from Horn's book is an examination of the work of the many others who have studied blended learning. Not even mentioning the seminal concept of blended learning as presented by Garrison and Vaughan in their 2008 book, is a major oversight, in my opinion. In order for blended learning to be effective in K12, we'll need to learn from the experiences of those who've used the evolving practice in higher ed just as higher ed will need to learn from K12.