Actively learn is an online ereader which is designed to help teachers interact with and engage students when reading text.
It has some great features such as the ability to use it with any online text or upload your own, annotation tools, embeddable questions and features that allow sharing with colleagues.
The free version works on any device, lets you use public domain books, lets you create your own layers of questions, and for American teachers has common core standards based grading. The paid-for version adds the ability to export grades and actively assisted book uploads although what they offer in the free version is really amazing.
This is an excellent tool for teachers who have a lot of students where English is an additional language although I see uses for this in every subject to aid comprehension of text. I could certainly use this teaching Physics and Environmental Systems where I could use it to draw students' attention to key points in the text.