Hello, community!

I made an er-diagram of an online bookstore(you can see it here: bookstoreEnglishPic.jpg - 4shared.com - photo sharing - download image
)

Bussines rules are very simple:
customers can made many orders, Item(in fact-as mentioned above- is a item in bookshop, mainly books, but it also can be, cd, dvd, e-book, paperback... ), there should probably be also many to many between author and item, but thats not the point probably at the moment.

It's a fact, that im still a begginer in database design, so i joined the community to improve my understanding... I would appeciate any comments, ideas, improvements....

I went through normalization process, i think it should be everything in 3nf.
Maybe there is a problem with the customer payment method.. I dont know how to solve this.

So, thanks for checking, i think there is still much to improve. Any comment is a good comment. Would be gratefull, seeya