IPA: /ɪnˈɡroʊsɪŋli/
KK: /ɪnˈɡroʊsɪŋli/
In a way that captures and holds one's attention completely; very interesting or absorbing.
The book was written engrossingly, making it hard to put down.
Engrossingly → It is formed from "engross" (from Middle English *engrosser*, meaning to absorb or occupy completely) and the suffix "-ingly" (meaning in a manner of). The word "engrossingly" means in a manner that completely absorbs or occupies attention.
Think of something that 'absorbs' your attention completely — that's what 'engrossingly' means, as it describes how something can capture your focus.