I'm not entirely sure as I haven't read 'aatish e ishq novel'. But often novels with 'ishq' (which means love in some languages) in the title might have love as a main theme. It could be about different forms of love like passionate love, unrequited love, or love in the face of difficulties.
Since I don't know the details of 'aatish e ishq novel', it's hard to say precisely. However, if we consider the general nature of such novels, it might explore the theme of love and its associated emotions. Maybe it shows how love can be like a fire ('aatish' can mean fire), burning and intense, and how it affects the characters' lives, their decisions, and their relationships with others.
Without having read 'aatish e ishq novel', we can only make educated guesses about its main theme. Given the title, love seems likely to be a central theme. It could also potentially touch on themes like sacrifice in the name of love. The 'aatish' in the title might symbolize the all - consuming nature of the love described in the novel. It could be that the characters are caught in a passionate love that is as intense and uncontrollable as a fire, and the story could revolve around how they deal with this powerful emotion and the consequences it has on their lives and the lives of those around them.