As a teacher I could see this work but only if
the textbooks use the advantages of being electronic & not just a PDF of treeware as ALL the so called etextbooks I have seen are.
Make them landscape so that they can be read with a minimum of scrolling ...
Make them interactive - embed video, animations, sounds etc to explain concepts...
Make exercises self marking (except for extended responses) & the document SCORM compliant so that it can be integrated in LMSs like moodle
Maybe better still mandate a LMS to be used and issue prepared courses.
And being electronic any intellectual property could be copied in a trice & the wriiters/publsihers would make no money