I would definitely say it can be stand-alone if you just want to add math and LA. There are a lot of activity and resource suggestions. If you do all of the suggestions and read all of the books you will have a very full schedule that includes geography, history, science, literature, etc. I am teaching it at our homeschool co-op and barely scratching the surface. I like it so much that we are going to use it as the backbone of our studies at home next year with my children (young K, 2nd, & 4th).
I have the pre-CD edition, but I did download the activity ebook which has the same content as the CD.