What should I do when reading a book? Should I analyze the language?

Since we acquire a language by getting lots and lots of input, the only thing you need to do is to read the book. Read as you would read a book in your first language. This is called extensive reading. You acquire words by seeing them used many times in different contexts. When you encounter a new word, many times you’ll be able to guess the meaning from the context. Encountering the word again in the future will help consolidate that word in your brain. If you encounter words or expressions that you don’t understand yet, skip over them. You’ll encounter them again in other contexts that will make their meaning clear. The alternative to extensive reading is intensive reading. Intensive reading is not a good idea. With intensive reading, you analyze the meaning of each sentence, make sure you understand the meaning of each sentence, how the grammar is being used, and look up unknown words or expressions. This has a number of problems:\n\nYou focus on language that’s far above your level. You spend a lot of time trying to understand things about the language that you are not ready for. All the time you spend doing this is not spent getting exposure to easier language that gives you plenty of opportunities to encounter the things that you are ready to acquire.\nIt’s very tiring, so you can only read a little bit each day. It even affects the rest of the learning that you do the rest of the day, since you are too exhausted to make the most of all the other input you may be getting during the rest of the day. You may even start developing negative feelings towards reading and start finding excuses to not do it.\nBy the time you’ve looked up and understood each word and expression that you don't know, you probably already forgot what the paragraph was about, or even the beginning of the sentence.\nYou are learning about the language, not acquiring the language. As we know, conscious understanding of the grammar rules doesn’t result in those rules being internalized and help you spontaneously understand and produce the language. More about this in the answer to What is the difference between learning and acquisition?. In addition, we know that things like learning words through translations or explanations and consciously thinking about grammar can impact fluency and make us internalize errors that are very difficult to get rid of.