I recently read the five existing books of George R. R. Martin's fantasy series, "A Song of Ice and Fire". It is perhaps better known by the name of the first book, "A Game of Thrones" (1996, 704 pages in hardcover). The following four books were "A Clash of Kings" (1998, 784 pages), "A Storm of Swords" (2000, 992 pages), "A Feast for Crows" (2005, 784 pages) and "A Dance with Dragons" (2011, 959 pages). As can be seen this is a very long series, over 4000 pages so far, and reading it represents quite an investment in time. Martin certainly has story telling talent and there are good things about the books. But overall I found the series seriously flawed and I can't really recommend it.
My first objection is to the overly ambitious scope of the story. It appears to me that someplace in the second book the author lost control and began multiplying characters and subplots beyond reason. I like a book or series to tie things together at the end and at this point this seems unlikely to happen.
A related issue is the way the series is written. There are numerous narrative threads and viewpoint characters and the books jump around among them. This is of course a common technique and is ok up to a point. But in my view this series has gone well beyond that point. Many of the narrative threads are largely independent and chopping them up and intermixing them just seems confusing and irritating to me. The problem is aggravated by the author's propensity for abandoning threads in cliffhanger situations rather than at natural stopping points which makes it harder for the reader to pick up the new thread.
My final objection is to the general tone and content of the series which is quite dark. The books assume a medieval level of technology (swords and crossbows) with some magical elements added. Considering what this period of human history was actually like it would have been unrealistic for the series not to have dark aspects. But the series emphasizes them in a way that I found off putting. It is not so much any one description of the strong mistreating the weak (often with sadistic cruelty) or of betrayal and treachery but the cumulative effect of many such descriptions over 4000 pages. When reading for enjoyment and entertainment I would prefer a bit less realism.
In my opinion the first book was the best. According to wikipedia the series was originally envisioned as a trilogy. I think Martin would have done better to stick with this plan. Authors sometimes have trouble coming up with satisfying endings to their stories. Greatly expanding the scope of the story postpones dealing with this problem but does not make it any easier.
So in summary, Martin is a talented writer and I certainly found parts of the books entertaining even compelling but ultimately I found the series disappointing. I am the sort of person with a compulsion to find out what happens next so I will probably read any additional books as they appear but if you aren't already invested in the series you might think twice about embarking on it.