They say that reading books is good. I'm not very smart perhaps because I don't read many books. I've almost never read a whole book from start to end. And I'm in my 30's. But I do read a lot of stuff in the web. But mostly short things. Not like long full books.

But isn't it the same thing? Or do I have to read whole books to get the same benefit

Well reading the internet is fine, HOWEVER it really depends on what your reading. Sometimes the internet is an unreliable source of information, so you have to watch and make sure what your reading has good grammar proper punctuation and stuff like that, because that's where your going to get the benefit from.
Also I would suggest reading a full book, just see how it feels, to me when I finish a book a feel accomplished and you might feel this feeling and like it, so try it for fun, but make sure you pick a good book.
Hope it helps :)

I would aggree it all depends on what your reading, not where you are reading it.
So if you where to go to proper places like CNN or Fox News, or Yahoo News. Or a proper online book seller like Kindle or Barnes and Noble to get your reading materal and read all the way though that then yes you will get the same benift. As you get the benfit from act of reading properly formated and correct information, or works of fiction presented as works of fiction but still have the same proper format that a printed story would follow.

So as a comparason one would get the same benift from gooing to http://www.nytimes.com/ and reading the artices there as they would gooing out and buying a copy of the New York Times and reading the paper. How ever if you where to instead go to a site like http://www.nationalenquirer.com/ where it can be dubous whether or not the facts are straight you won't get the same benift and might actually end up worse off if the stories you read about really are just stores and not fact but where being presentd as fact.