Thanks for trying out mBook. Can you send me the URL to my email, firstname.lastname@example.org? I would like to check a few things, but actually you may also help to see if your Moodle is of version 1.9.x, debug mode OFF, English as default language, JSON is installed, our "mobile" folder is installed, and of permission 640 or 644 or 777, etc.
If it is Moodle 2.x, our coming release will support it with another web service folder, MWS, instead of "mobile". Please have the above examined first, or you may send me the URL. Thanks