Using Quotation Marks
Using an Asterisk
One of the best indicators of whether or not your book or e-book is considered a "scholarly" source is its publisher. Academic publishers such as Wiley, Taylor and Francis, Brill, and Routledge (to name a few!) and university presses (Oxford University Press, for example) are responsible for publishing almost all of the scholarly books and e-books that you'll need to use in your research projects.
Check the lists linked below if you aren't sure whether or not the publisher of your book is considered scholarly or academic. If you don't see your publisher listed, you can always reach out to your professor for their input, as well.