Sorry but I have to join the bashing. Some years ago I wanted to get better at programming so I picked up his material. It took me less than 10 hours to realise

Sorry but I have to join the bashing. Some years ago I wanted to get better at programming so I picked up his material. It took me less than 10 hours to realise he was just peddling the same thing as the Gang of Four book that was released in 1994. I'm sorry but I'm not interested in your design patterns that only need to exist because your OOP language lacks more powerful constructs. A lot has happened in terms of language design since 1994. If you are still stuck in Java 5 or something like that, please go ahead and read his books otherwise you will be better served by learning a modern language like Swift, Kotlin, Rust, etc...