Utopia was officially released in the year 1516, becoming one of More's most popular books to this day. The novel is a work of fiction and serves as a socio-political satire - meaning it critiques in an exaggerated way.
The book starts off with Thomas More arriving in Bruges, eventually meeting up with his group of friends, one of them being an explorer. Together, they debate whether or not the knowledge gained from exploring should be used to improve society. Raphael Hythloday, the explorer, believes that as long as the truth exists, everything will remain pure and true. On the other hand, More sees purity as something that cannot be achieved. The two friends have contradicting ways of thinking, bringing up different scenarios such as thieves, eviction and greed, to prove the other wrong. Greed is a reoccurring theme as the idea of how people in power only care about money, not people, is discussed. Later on, Hythloday tells More of a crescent-shaped island called 'Utopia.' He explains its origins, saying that it was once a barbaric island that turned into heaven overnight. This is obviously impossible, Utopia being a clear symbol of the fantasy-like country never being able to manifest in a real life society. More sees Utopia as absurd since the way it's described is completely different from the laws he lives with. In the end, one side is supposed to represent one's idealistic approaches to problems while More is the representation of how reality corrupts it.
Overall, the theme of Utopia is how an ideal society for mankind is unattainable; it's merely just a dream that not even the most determined can reach. The crescent-shaped island is the embodiment of these wishes, where poverty and corruption are nowhere to be seen. Hence, the reason it was called 'utopia'. In Greek, it can be translated to 'no place' or 'nowhere', further establishing the fact that a place like the island described can never truly exist, no matter how hard we try. Greed, pride, and unholy desires will follow behind the steps of humanity; that's the message Thomas More was trying to convey through this book.
Above is a photo reference of the island being communicated about in the book