Hi Maddie, I just joined HubPages, and saw you're hub and wanted to participate and answer your question. First, I loved the first season so much, I watched it several times and it became evident, at least to me, that much more was going on in the background stories, which only can be found in the books. So, off I went to read the first book of the series, "A Song of Fire and Ice". I was hooked! Tons of details and the best part of reading the book was all the extra information you learn about your favorite characters!
Obviously, reading just the first book of the "Song of Ice and Fire " series was not enough for me, so I bought the next 3 books because book 5 wasn't release yet. By the time I finished book 3, I felt I was reading the best thing since sliced bread! Finally I read books 4 and 5...and like many other readers...now I'm waiting in a state of desperation for author George RR Martin to write and finish the next two books! The waiting is agony!!
After all of THAT, the second season on HBO began in 2012, and I watched with eagle eyes...and this is my answer to your question. The HBO series and the books are completely different mediums of expressions...books have the leisure of expanding in great details such things as why the Direwood trees (the white trees with red leaves) look the way the do and their meaning and purpose, or who are the "First Men", that is not clearly explained in the HBO series by Sam Tarley. In the books we understand the "where, why, what and how" things are, while in the HBO series, mind you a different medium, is restrained by the visual aspects of the story, let alone the budget it takes to create such a complex world. I enjoy the HBO series very much, its why I got hooked in the first place, and I'm looking forward to season 3, because for all those who haven't read the books are in for an amazing time in HBO's season 3. But deep down inside, I'm looking forward to books 6 and 7.
Remember....Winter is coming....