Gustavo I read only this one. It was my first Bernard Cornwell book ever. I didn't even know that it was a serie. I think that the story of this book is quite independent and I like it a lot. Go ahead.
Will I think you will appreciate aspects of the book more, if you've read the earlier titles in the series first. To give just one example, the Scottish character, Robbie, has sworn a vow not to fight the English. Without having read the previous book(s), you will have no clue as to why he made that oath in the first place, or why it means so much to him.
Jalen Anderson I read all of the Grail Quest books, and I don't feel they are very necessary to follow 1356. There are a few characters you may not know a whole lot about; however, it won't change your ability to comprehend what is going on. I would still say Archer's Tale is the best of the 4 books, however. It's one of my favorite all time books. It's probably because I really like traditional archery.
Ed I agree with Gustavo. I've read all the Grail series plus just about everything else Cornwell has written. This book can definitely stand on its own. It may be the best in the series.