Seeing as i've read books that are 7/800 pages long i'm not really put off by size unless it's like 1500 pages.
Like jjapples said, George Martin's stuff is easy to read. He's very reader friendly, he's not trying to reinvent ways to construct sentences. His writing flows together. That said, he's pretty much what I'd call a master of the language. He can create some vivid scenes without a doubt, stuff that sticks in your mind and lingers. His books aren't small save A Feast for Crows, the fourth.