You'll still need the Who, When, What and Where when referencing a physical book as well as an online or eBook. With the online version, you'll need to add the electronic elements. See examples of both below.
ADEBAJO, A. and DUNKLEY, L., eds. 2018. ABC of Rheumatology. 5th ed. Hoboken, NJ: Wiley Blackwell.
BREEZE, M., 2015. Seriousness and Women's Roller Derby: Gender, Organization and Ambivalence [online]. Basingstoke: Palgrave Macmillan [viewed 11 June 2018]. Available from: http://qmu.eblib.com/patron/FullRecord.aspx?p=4082426
CHABNER, D.-E., 2016. The language of medicine. 11th ed. St. Louis: Saunders.
HUTCHINSON, K., 2018. Leadership and Small Business: The Power of Stories [online]. Cham: Springer International Publishing [viewed 11 June 2018]. Available from: http://dx.doi.org/10.1007/978-3-319-64777-7
ISENBERG, N. W., 2018. We'll always have Casablanca: The life, legend, and afterlife of Hollywood's most beloved movie. New York, NY: W. W. Norton & Company.
KHAN, K. S., KUNZ, R., KLEIJNEN, J. and COOMARASAMY, A., 2011. Systematic reviews to support evidence-based medicine: How to review and apply findings of healthcare research. 2nd ed. London: Royal Society of Medicine Press.
MUMFORD, A. and HONEY, P., 1982. The manual of learning styles. 2nd ed. Maidenhead: Peter Honey Publications.
MUMFORD, A. and HONEY, P., 2000. The learning styles helper’s guide. Maidenhead: Peter Honey Publications.
NAPIER, J. and LEESON, L., 2016. Sign Language in Action [online]. London: Palgrave Macmillan [viewed 11 June 2018]. Available from: http://dx.doi.org/10.1057/9781137309778
PATTERSON, D. and AFTEL, M., 2018. The Art of Flavour: Practices and Principles for Creating Delicious Food. London: Robinson.