I'm deliberately not reading Game of Thrones or Song of Ice and Fire or whatever the book series is called, though I'm itching to do so. Two reasons, one: it's nice to have a complete series to read in its entirety without having to wait months or years for the next installment, I think the experience is so much more intense that I think I'm willing to wait until Martin puts his final wrap around it. And two: well, there's a lot of really good fantasy book series' around but only one really good fantasy TV series, i.e. Game of Thrones so I don't want to detract from it's effect by fore-knowledge or be distracted by discrepancies.
Anyway, talking of really good fantasy series I've been re-reading Katherine Kerr's Deverry series, the first 4 anyway... good stuff, very Celtic.