Power - up system. Most of these novels have a system where the main character can continuously increase their power, like in 'Solo Leveling' where the protagonist levels up. This gives a sense of progression and excitement.
Novels similar to 'Solo Leveling' typically have an element of the underdog rising. The protagonist is often underestimated at first but then surprises everyone with their rapid growth in power. There's also a prevalence of a unique world - setting, whether it's a fantasy realm with magic and monsters or a post - apocalyptic world with new rules. These novels also tend to have a large cast of supporting characters that interact with the main character and help or hinder their journey to power. Additionally, the plot usually revolves around the main character's quest for power, revenge, or to save the world. For example, in 'The Beginning After the End', the protagonist is reincarnated into a new world and has to start from scratch but eventually becomes a powerful force in that world. The story is filled with his training, battles, and interactions with other characters which are all hallmarks of novels like 'Solo Leveling'.
A common element is a powerful protagonist. In 'Solo Leveling', the main character becomes incredibly strong. Other similar novels also tend to have a lead character with extraordinary abilities or the potential to grow into a very powerful being.
One similar novel is 'The Beginning After The End'. It also has a protagonist with a journey of growth and power - building. The story is set in a magical world with various races and complex power systems.
Some novels similar to 'Solo Leveling' are 'Tales of Demons and Gods'. The story follows the growth of the protagonist in a world full of challenges and he has to constantly level up his abilities. 'Martial Peak' is also a great choice. It shares the theme of the main character's arduous journey to reach the peak of power, with lots of battles and character development along the way. And 'I'm Really Not the Demon God's Lackey' has a unique take on the idea of power growth and a really interesting world - building.
Another one is 'Overlord'. It shares the aspect of a powerful main character in a fantasy world. The protagonist has overwhelming power and has to deal with various challenges in a new and strange world, just like in 'Solo Leveling'.