If I have to carry it around and it weighs heavier than a brick, if I have to forgo good short stories and novellas for it, it jolly well be more than just good.
Thankfully, the latest Van Gogh biography fits the bill. Nevertheless more than half the reading is still done at home. I couldn't read it while commuting because it's simply too heavy to carry around.
On the other hand I have a very compressed and relatively light paperback copy of Brothers Karamazov, but it is still moving *very* slowly...
Generally yes...long books put me off reading for these reasons: the weight of the book, the amount of information (history, family saga etc.), langauge that is usually not concise(unlike Orwell, Yates, Hemingway -- sharp and to the point), and the difficulty of sustaining interest over every 50 pages or so.