I think most people who have "read" Mein Kampf, like I have, have read bits and pieces of it and found it too turgid and unreadable to get through in its entirety. It's much like Das Kapital in that way, in that it has a lot of "deep" ideology but it's obviously shit because these ideas have all been tried out and never ended in anything but disaster. (Actually Das Kapital is even worse about this.)
Too bad the actual Communist Manifesto was brief, concise, and came across convincing. That book almost certainly got more people killed than Nazis ever did.