Reading teaches you new words and perspectives. It helps strengthen language and sharpens sentence structure. It gives you a better command of the language. All of these are critical to being a good speaker.
Explanation:
The mind is a muscle, and just like all other muscles, it needs to be exercised to grow. Reading is a way to help strengthen your mind.
Reading can help you remember more material, comprehension is also an important life skill that you need to use almost everywhere. Also, reading is fun, finding new words and phrases expands your vocabulary, and mind in general. Reading helps with thinking in a more logical or imaginative way (depending on what material you read).
The author is writing the passage to talk about Conrad's life as a black man in Nigeria and the way he feels about the other black people's lives in Nigeria too.
