requires a lot of data and it requires a lot of analysis. we're getting closer to what we call personalized health care. similarly with education, we simply didn't know when pupils read textbooks what part of the textbooks they liked most, what made most sense for them and with which parts they struggled. now with ebooks like the kindle or the ipad or other tablets, we can gather that data and then analyze it. so for the first time textbook authors, educators, teachers, and schools will find out what educational materials really work. >> how do you know when somebody is reading a book on a kindle? >> so, for example, in our book that we just did, amazon tells us what people underline most in our book, and i would never have guessed the sentences that people underline most. so it is a unique lens into how readers understand our books and it's phenomenally helpful for the authors but also for those