ebook textbooks?

[ncaraway]

There seem to be almost no end of "how to" ebooks for teachers. What I find lacking are textbooks in ebook format that I can use. My goal is twofold:

1) to minimize the number of books I have to lug around, especially for 1:1 classes where I mix and match textbook content to customize lessons

2) to minimize the cost for students since ebooks are usually considerably less expensive than bound books.

I currently use a mix of the following for my 1:1 students (depending on their needs):

bound:
-The Ins and Outs of Prepositions (Yates)
-Oxford Picture Dictionary
-Fundamentals of English Grammar (Azar)

ebook:
-Compelling Conversations (Roth)
-Write Right (Giles)

If you have other recommendations (for both ebooks and bound books), I hope you will share them.