I read this series (and the Kingdom books) for the first time when I was 12 and I absolutely loved them. I recently bought the whole series and re-read them and, at 18, I love them just as much now as I did 6 years ago!!!
There's 12 books total. 6 kingdom books and 6 Knights of Arrethtrae books. They're all allegorical, but In the kingdom series allegory, the people and events in the books are based on actual people and events from the Bible, while the Knights of Arrethtrae series presents biblical principles allegorically. While reading them, I loved trying to figure out who or what the different characters and events represented and then checking the discussion answers to see if I was right.
The books are set in medieval times and has fantasy mixed in, but there's no witches or magic. So if you like stories about kings and queens, knights in shining armor, evil lords, castles, and dragons, and you haven't read this series yet, then you need to now!!
Getting this set of 6 books on Christianbook was the best deal I found. There was like 3 books where the pages were wavy and puffed, like it got kinda wet or something, so my mom called and they replaced those 3 and I didn't have to pay for the extra shipping or anything. So, I really like Christianbook.com and I hope my review helps(:
My 12 year old is in love with this series. She read the Kingdom series and enjoyed it so much that she had to read these. They teach so many wonderful values! I couldn't be happier with these books. The story has enough appeal to keep both boys and girls interested in the books. My 10 year old daughter has started reading these as well.