This is a wonderful book written by Guy Gavriel Kay, who had the honour to work with Christopher Tolkien on the Silmarillion who went on to become an accomplished author in his own right. I enjoy many of his works as they are fantasy with very interesting parallels to our own medieval times.
The Last Light of the Sun has a very strong celtic theme to it as well as familiarity with our own roots. I read this some years ago, not too long after it came out.
Guy Gaviel Kay's website can be viewed here at http://www.brightweavings.com/