Book Creator for Chrome is now available, and it has some amazing features.
Google Image search
"When you tap the + button and select Import, you can now search for images on Google. Rest assured that safe-search is enabled, and all the images have full permission to be used in your books. You can also disable the feature altogether in a library's settings if you prefer students to only use their own images."
It is a free/paid tool. Teachers can create a library of 40 books for free. That's ok, though, because you can export finished books to other places and remove them from Book Creator. HERE is the price list, but you know I always try to use free tools when I can!