You can access your ebook without an internet connection.

• If your ebook is fulfilled through VitalSource, then you will need to download the Bookshelf app onto your computer, tablet, or mobile device. For more information about the Bookshelf app, visit: https://support.vitalsource.com/hc/en-us/categories/360001056774
• If your ebook is fulfilled through RedShelf, you can create an offline session on the sidebar menu. For more information about offline reading with RedShelf, visit: https://solve.redshelf.com/hc/en-us/articles/115003794953-Offline-Access