I found a site for middle- and high-school E-books. They look useful - one of them covers labs for class - with PICTURES of the setup of equipment. That part, I found a GREAT idea - how often have you hesitated to include a lab, because the diagram of the setup wasn't clear?
These books are, as the name suggests, modifiable. Over time, you can create a book customized for the course you teach.
Here's the link to the site for high school physics books (called FlexBooks.
Here's the main site.