In a manga, a smartphone could fall in love by being personified and encountering experiences that trigger emotional bonds. It might interact with other objects or characters in a way that mimics human romantic connections.
It could be a hit depending on several factors. A unique plot, well-developed characters, and quality illustrations could all contribute to its success. However, competition in the manga market is fierce, so it's not guaranteed.
In this novel, one of the important characters could be the creator figure. Their relationship with the falling angels and their reaction to the fall would be crucial. The leaders among the fallen angels are important too. They would be making decisions and leading the others in their new, fallen state. There might also be angelic messengers who try to bridge the gap between the fallen and the remaining angels, with their own dilemmas and challenges in this difficult situation.
The main themes in 'the fall of angels novel' are likely to include the nature of sin. Since the angels are falling, it represents a foray into immoral or wrong actions. Also, the theme of redemption might be present. Even though they have fallen, there could be a possibility of them seeking redemption. And power dynamics is another theme, as the fall may be related to a struggle for power among the celestial beings.