Thanks for reaching out to OkadaBooks. To disable "AVAILABLE IN APP" kindly follow these instructions below:
1. Go to publish.okadabooks.com
2. Sign in with your username and password.
3. Go to PUBLISH and click on my Publication
4. Click on the pencil icon next to the title of your book.
5. Scroll down and untick disable from webstore shown below. (Note that your book can now be read via the OkadaBooks app and website).