You'd have to be incredibly ignorant to suppose it to be a work not worth reading. It is not the best piece of writing, not even of Marx's, but its influence on humanity is enormous; that should suffice for the value in reading it.

Even if you completely disagree with every single word, it's still good to know what it actually says, if for no other reason than to be better equipped to argue against the parts you disagree with. Same thing for the Bible. It's one thing to know it backwards and forwards if you're a "true believer", but you certainly can't hope to hold any sorta worthwhile discussion on the topic with someone who is if you've never even read the thing. Knowledge is just another form of power; one that many willingly and actively choose to deny themselves for some reason.