Why, are you illiterate or something?
Ad hominem modded "insightful"? Seriously, the mods are feeding the trolls now? Alas, since this is modded up, I'll risk a response....
No, seriously -- if you have to go look up stuff often enough for that to be a big deal, then (a) the book is too hard for you
Some people like to challenge themselves once in a while. By your logic, we should never move beyond our elementary school readers.
and (b) you're missing the point of reading. You'd lose sense of how the story flows if you keep starting and stopping like that.
Gee, there's only one possible "point of reading"? And here I thought that one of the primary "points of reading" was to understand what the author was saying... which you can't very well do if you don't understand the words.
You're also talking about "stories" -- what about non-fiction? Or what about classic literature, which may use language a bit differently?
In all seriousness, one of the primary reasons why the written word was invented was so it could preserve information... whether that be stories or non-fiction or whatever. Why? So that other people can learn about it. The idea that reading only functions as entertainment is a modern phenomenon.
And if you're using reading to learn things, you should be prepared to encounter new ideas, which often may involve new words. I have taught graduate-level courses at universities, and one of the things I strongly encourage students to do is look up recurring words that they don't know. If you don't do that, you won't understand the text. And part of the learning process is often having a challenging reading that allows you to expand your ideas, which usually involves some new vocabulary at the same time.
When you run across the occasional unfamiliar word, it provides a better experience just to figure it out from context and move on.
Yes, that's a great exercise, and if you're in the middle of a fast-paced novel, it's probably a reasonable idea. But if you're actually trying to understand what an author is saying, and there's this word popping up a dozen times that you don't know, simply guessing what it means is missing an opportunity to learn something.
And recurring words are great for that kind of exercise, because it provides periodic reinforcement, which is one of the keys to learning natural language and recalling new things. Most authors -- even those who write "stories" and fiction -- tend to have "pet words" that aren't part of the standard core vocabulary everyone uses. When you see such a word and look it up, each time the author uses it again you'll reinforce that word. Suddenly, by the end of the book, you'll have expanded your vocabulary by a dozen or a few dozen words. (And you're more likely to remember the meaning than if you had just memorized the word for a vocab test or something -- seeing practical usage will aid recall.)
How else does one ever get to read books that are "too hard for you," as you put it? Or should we just ignore such books? By this logic, unless you were born with a giant vocabulary or hang around with people who use big words all the time, you're obviously not destined to read such weighty tomes....