Book List for History

I apologize if this question is answered somewhere else. I have just ordered our first History lessons beginning at Genesis. Using the suggestions for where to find the books for History, Geography, and Bible I also ordered the additional books that SCM has. However, I also see a list of books that we can find at a local book store. I am wondering if it is a good idea to purchase all of the required books because I will be using them throughout the year or will using a library be an option for these additional books?