As for Tubby - I've done a little bit of studying Marx as if he were someone to be studied. Deadly boring. I'm not sure what it is you're looking to learn, really, but if you have any curiosity about Marx as anything other than a dead bloke who wrote some stuff ages ago, your rule is going to get in the way.

Try "A Rebel's Guide to Marx", by Mike Gonzalez, as a starter. Though Eagleton's isn't the worst book.