Hi,
I think The Sword of Truth is recommended in the GoT books themselves if I remember right. I haven't read that yet myself so I don't know. The are some good suggestions above too.
I can highly recommend the works of Robin Hobb though. If you don't know the author, I suggest you don't read up on them before reading the books. You'll see why I say that once you're reading them. Apart from The Soldier Son trilogy, they're all part of the same series. I think all of the books are on this website. There are 3 main trilogies before a quadrilogy was added and then a related novella - and more books are being written at the moment despite the author saying years ago that the series was ended.

I'm really looking forward to them!
You'll start with the Assassins Apprentice - have a change of scene for the second trilogy called The Liveship Trilogy, then see things hook up again in the third, Tawny Man, trilogy.
I adore these books and have come to love George R R Martin's GoT books as much. They are 2 of my 3 favourite authors and worlds.
The reason I recommend them is because they are just as involved and detailed as the GoT books. Not just the style of writing but the worlds are just as developed and the characters believable as I believe you want or will enjoy.
Also, maybe more importantly, there are many themes that cross over with the GoT books. There are royal intrigues, the life of bastards and their special importance, the Wit rather than Wargs and similar powers like the Skill, mysterious ancient ruins, castles, a medieval "feel" to the history and technology, magic, assassins, poisons, love stories, hate stories, premonitions and predictions, catastrophic volcanic Doom of old, sword fights, prophets and prophesies, duels and trials by combat, pirates, magical creatures (some also called Others), wolves,... *dragons*... of course!.... and so much more.
That's at least 14 nicely fat novels to get you on your way.

And like GoT you may find yourself wanting to re-read them straight away so you can pick up on the details you missed the first time round.The main theme itself is a mix of dragons and playing for the thrones of various countries and their Dutchies.
There are some books recommended above that I know are good but I don't see how they're like Game of Thrones. The Pullman books for instance - completely different style and really not any themes along the lines I've mentioned. They're good but I wouldn't say they're "like" the Game of Thrones series on paper or on screen. Much as I loved the Xanth series while growing up, I would say it's nothing at all like what you're after. Robin Hobb's books - I *would* say those are "like" Game of Thrones.
So far it's the closest thing I know of to recommend to you. I can recommend lots of things but not anything else I feel is "like" GoT. I haven't read all of the other suggestions above so I might try them myself. I was actually looking for a series like Robin Hobb's when I eventually found Game of Thrones; although none of the recommended books I got were actually like what I was after.
I'm probably going on about them too much now but I really, really can't recommend these books highly enough. lol

*grins*
Don't forget there are some short stories that go with the Game of Thrones books. The Tales of Dunk and Egg I think they are. They are what lead me to the main series.
And don't forget that the Soldier Son trilogy isn't part of the same series as well. It's well worth a read (although the first book seemed to be all set-up for the real action) and still contains magic - but there are no dragons and it's set in a completely different world and "time" and has different themes. Still a fantastic story though and I do recommend it - but for different reasons.
Is it similar themes you're after or have I missed what you want?

I hope I've answered your question the way you wanted. I actually replied to this thread when you first posted but my post didn't go up for some reason. I need to request related books if you want to chip in some WRZ $ to it.

I'd like to see what the comic book version is like too.
Send me a PM if you need or want to about getting these books.

And please let us know if we've been answering your question asking the right lines. It can be hard getting recommendations at times. Still - it's amazing what you can find even if you've gone through a bad bunch and keep going till you realise the new book you just picked up is so good you're several chapters in before you know it.

Okay - hope you read and enjoy those books as much as I have. Same goes for anyone else who reads this. lol And let me know what you think of them.

Have fun. x