Definitely 'That Time I Got Reincarnated as a Slime'. Rimuru Tempest starts as a slime but quickly builds a powerful and unique kingdom. It has a great mix of action, comedy, and kingdom - building elements. Rimuru's leadership and his ability to bring different races together make for a very interesting read.
One great kingdom building light novel is 'Overlord'. It features a powerful character who is transported into a game world and has to build his own kingdom. The story is full of strategic planning, interesting character interactions, and unique world - building elements.
'A Song of Ice and Fire' is also great. There are multiple kingdoms vying for power. Westeros is filled with complex political intrigue among the Seven Kingdoms. Each kingdom has different ruling families, climates, and resources, which all play into the power struggles and the building (and often destruction) of these kingdoms.
A great kingdom - building light novel often has a strong protagonist. For example, in 'Overlord', Ainz Ooal Gown is an overpowered character which makes his attempts at building a kingdom full of interesting challenges and solutions. His power allows him to face threats head - on and also attract various followers.
'How a Realist Hero Rebuilt the Kingdom' is also worth mentioning. The hero is summoned to a fantasy world and has to use his real - world knowledge, especially in economics and politics, to revive a declining kingdom. It's interesting to see how he tackles problems like food shortages, trade, and military organization.
'The Wheel of Time' can be considered. It has various nations which are like kingdoms in a sense. They have their own ways of governance, magical traditions, and social hierarchies. Rand al'Thor's journey often involves dealing with these kingdoms, their rulers, and the balance of power among them.
One popular one is 'Overlord'. It features a powerful sorcerer who gets trapped in a game world and begins building his own kingdom. Another is 'Re:Monster' which has an interesting take on the isekai genre with the protagonist being reincarnated as a goblin and working towards building a great goblin kingdom. 'That Time I Got Reincarnated as a Slime' is also great. The slime protagonist gradually forms his own unique and powerful kingdom through various adventures and making allies.
Definitely 'Lord of the Mysteries'. It has a unique setting where the main character has to navigate a complex and mysterious world. As he progresses, he builds his own group and influence, which is similar to building a kingdom. The plot twists and the rich lore make it a standout in the genre.
One great kingdom building web novel is 'Release That Witch'. It has an interesting premise where the protagonist is transported to a medieval - like world and uses his modern knowledge to build a powerful kingdom. The character development is well - done, especially for the witches who play crucial roles in the kingdom's development.
One of the must - read light novels could be 'Sword Art Online'. It has an engaging story that combines virtual reality and high - stakes adventure. The characters are well - developed, and it has a large following.
I would recommend 'The Rising of the Shield Hero'. It has a great concept where the hero is initially betrayed but then rises to power. The world - building is excellent, and it explores themes of trust and redemption.