The main themes include transformation. A slime is a simple form at first, but it may transform in different ways throughout the story. There's also the theme of exploration. It might explore new lands, meet new species, and learn about the world it lives in. Additionally, the theme of power - acquisition could be present as it tries to become stronger to protect itself and its friends.
I think the slime is the most captivating character. Since it has to start from such a basic state and build itself up. There could be a fierce warrior - type character who initially underestimates the slime but then becomes its ally. This contrast in their relationship makes the warrior character quite interesting. Also, a kind - hearted healer character who helps the slime in times of need can be really appealing.
There's no definite answer without actually reading the 'My Life as a Slime Novel'. If it contains only simple themes like the slime's exploration of its surroundings, making friends in its slime - world, and learning new things, then it should be suitable for all ages. But if there are elements such as complex politics or mature themes that are not appropriate for younger readers, then it may not be. However, given the concept of a slime as the main character, it has the potential to be a very family - friendly novel.
One of the important characters is Shizu. She has a connection to Rimuru's past life. Rimuru himself is the central character. He is a slime with a human mind, which makes his character very interesting. There are also demon lords like Milim Nava. She is a powerful and somewhat unpredictable character. Her interactions with Rimuru add a lot of flavor to the story. There are also the dwarves, like Kaijin, who play important roles in Rimuru's development, for example in helping him with creating his town.
[The recommended novel: "Comic: About My Reincarnation as a Slime". This is a light novel, a derivative Doujinshi novel. The protagonist reincarnates as a Slime from another world. He has a flexible moral bottom line and kills evil people to save people in need.] The novel took the form of an infinite stream and traveled through many worlds, including "Did I Make a Mistake in Seeking an Encounter in the Dungeon","Fate/Zero", and so on. I hope you like my recommendation.
The main plot involves a man who gets reincarnated as a slime. He starts from a weak state and gradually grows in power. He befriends various monsters and builds a community in the new world. For example, he forms alliances with goblins and helps them develop.