IPA: /ˈiːbʊk/
KK: /ˈiˌbʊk/
A digital version of a book that can be read on a computer or electronic device.
I downloaded an ebook to read on my tablet during the flight.
Ebook is formed from "e-" (a prefix derived from the word 'electronic', meaning relating to electronics) and "book" (from Old English "bōc", meaning a written work or text). The term "ebook" refers to a book that is available in a digital format, specifically one that can be read on electronic devices.
Think of 'electronic' ('e-') to remember that an 'ebook' is a book in a digital format.