Brilliant alternate-history/fantasy author. I finished reading "The Lions of Al-Rassan", based in the Reconquista period of Muslim Spain, and I have to say that it is one of the best books I have ever read. The characters are morally ambiguous, the plot is very realistic and never becomes melodramatic, and the writing style is very descriptive but it never turns into purple prose. It's also genuinely funny - a lot of other books (like A Song of Ice and Fire) are funny but the humour is generally limited to irony and the mocking of other characters, with one-sided laughter and the other side taking themselves way too seriously. Al-Rassan is one of the first books I've read where both sides laughed at themselves and each other; the banter is really quite relieving in contrast with the tragic themes of loss and death that permeate the book.
He has also written other alternate histories: the Sarantine Mosaic (Byzantine Empire), Tigana (Provence in the Albigensian Crusade, except with magic), and Under Heaven (Tang dynasty China) come to mind. I've yet to read his other books, but if Al-Rassan is anything to go by, then I whole-heartedly recommend that you read his books!