I always found Caesar's Commentaries to be a bit boring in class. The beauty of Ørberg's work is that the stories are original and have been supported by other authors. It seems to me that Familia Romana, the first book by Ørberg, pretty well covers Latin grammar as well as introducing about 1,900 words. The second part, Roma Aeterna does include original texts. The Fabulae and several other books provide a bridge from Book One and Book Two. So, I wonder, why recreate the wheel? Is it just to teach to the AP test?