Well, true. It has a bit of dark and gritty in it. There is an incestuous couple, a few torture scenes here and there(which are honestly more visualized in the TV show than in the books), quite a bit of rape, and not so much murder as just people dying because it's war. And yes, characters - big, major characters, ones that you enjoy and grow to love - do die. Often, and without much warning.
However, I am 5 books in(there is a total of 7 books, and 2 of them haven't been written yet) and my 3 favorite characters are still very much alive and kicking. So I would definitely not say that there is "no hope" - in fact, there is a lot of hope, even down to the point where it's pretty much "which faction are you rooting for". And most of all, Game of Thrones\ASoIaF is all about political intrigue. When it comes down to it, it's pretty much all about who's going to sit on the iron throne. And it's awexome beyond words.
Without venturing too far into spoiler territory, I can tell you that Ned Stark(and the Starks in general), Jon Snow and Daenerys are all very much "good" characters, so to speak, in that they represent goodness, hope and justice\fairness, whereas most other characters tend to be pretty much either assholes or tricksters(Tyrion Lannister being another favorite of mine). Also, there is a lot of "redemption" going on in the latter books, with characters that you hated suddenly being the good guys, trying to atone for what they've done.
Seriously, if there's any book\book series that I would say is absolutely a must-read, A Song of Ice and Fire is it. I have never heard of a person who's read ASoIaF\watched GoT and honestly said: "Nah, this isn't for me. I don't like it.". I don't think that's physically possible.