Praise be to Allah.
1. With regard to reading these stories, this is a waste of time. People are deceived by the idea of “free” time, for it is one of the things about which they will be questioned on the Day of Resurrection.
It was narrated that Ibn ‘Abbaas (may Allaah be pleased with him) said: the Prophet (peace and blessings of Allaah be upon him) said: “There are two blessings which many people do not make the most of: good health and free time.”
(Narrated by al-Bukhaari, 6049)
Abu Barzah al-Aslami said: the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “A person will not be let go on the Day of Resurrection until he has been asked about his life and how he spent it, his knowledge and what he did with it, his wealth and from where he earned it and where he spent it, and his body and how he used it.”
(Narrated and classed as saheeh by al-Tirmidhi, 2417)
2. As for writing these stories, in addition to the above point that it is a waste of time, it also involves a second forbidden matter, which is lying; lying cannot be avoided if one is to write in an attractive and compelling manner about things that do not exist.
If a person has to write, then let him write about something that is real and happens in the lives of people nowadays, writing about things that really happened to him or to others, from which lessons can be drawn. Or let him write by way of giving examples and allegories, stating that in an introduction. Even better than that, let him write about the true and sound stories that have been narrated in the Qur’aan and Sunnah, or about the lives and biographies of great Islamic personalities such as the Prophets, scholars and righteous people, or stories of earlier nations of whom Allah has told us, in an exciting and interesting style in which there is no distortion or addition of things that did not happen and things of which the author has no knowledge. They should also be narrated in an easy and straightforward style that is appropriate for children, and in his books he should promote good character and virtue.
For more information, see question no. 3324.
And Allah knows best.