I am writing this for the whole series. Honestly I was not very thrilled after the 1st book, but I forced myself to go forward, hopping for the best. 1st person dialog is used, which makes a good development of the main character, however, because everything is seen through the eyes of one person, the rest of the characters lack depth, and it is hard to create a bond with them. As you encounter them many times through the story, you get to know them better, however, it is not ideal. You should keep going after 1st book, so do not give up just yet.
The writing is getting better as the story goes on, less cheesy sex, and more action and adventure. In the last book the author gets half the book from 3rd person perspective, which is clearly an improvement in the writing style, and lets you get to know Mordred better.
The narration is quite good, but it takes a little to get used with the narrator, which has some interesting intonations. The last 2 books are narrated by somebody else, which is not a plus(even if narration is good), as you get used with the original one through the previous 5 books.
This being said, I recommend the books, and looking forward to follow the story into the Avalon Chronicles!