The model answers point to "accumulation of knowledge over a long period of time". "He must read" refers to a constant habit. "He must have read" refers to his entire life in the past. Your answer is not wrong, but it points to recent and current activities. If I use this sentence as an example, then your answer will appear more suitable: "I have seen him very often in the local library in the past two months. He must be reading a lot of books."

Thank you, Alan! Know/knows - yes, some times I forgot add "s" :)

Yes, your sentence will work in some contexts. But the other two versions are probably used more often. Also, note that "Some guy know many interesting things" does no follow standard grammar. It should be "Some guy knows..."