Gavin Menzies is a person who wrote some books about the history of the world. He likes to research things that happened a long time ago and figure out what really happened. He is especially interested in things that happened on the ocean, like when people sailed boats.
Sometimes, Gavin Menzies' ideas are different from what other people think based on the facts they know. Some people believe what he says, and some people do not. It is like when two friends argue about what happened in a game they played earlier in the day. They both have their own ideas about what really happened because they saw things differently.
So some people like Gavin Menzies' books because they are interesting and tell a different story. But other people do not believe everything he says because it is not always supported by evidence.