In the Hall of the Dragon King (Dragon King Trilogy book 1) by Stephen Lawhead

This book has a very Robin Hood feeling to it. The King is captured while leading the army in a crusade, His brother tries to take the kingdom for his own, A loyal nable becomes an outlaw leader etc. But this is only a basis and the book is actually about a temple Acotyle Quentin who is sent to carry a message to the Queen when a dieing knight arrives at the temple.
An this leads him on a quest to save the king changing his life forever. This is a good read, most of the characters are pretty standard characters that you would expect in an arthurian story. Nimrood is the the standard villian all gloat and no thrust. But I really like the book it is an interesting and entertaining read and one of the first fantasy books I read.