WikiBook on European History
Here is a complete e-book on European history. It is certainly not as long as your students' textbooks, but it does give a great overview and might be useful as a resource. It would be especially good for review material. Here also is the IB book for European History. I found these two after a little clicking that started with a tweet from MisterHistory. You can follow my tweets on the sidebar of this page or by going here and signing up for them.