Book 6 - Is a Hit!
You are more than halfway through! So give yourself a HUGE BRAVO! And keep on. You are building your language ability in all ways. You are used to the method by now and should feel comfortable when you "don't know something" understanding that you simply continue, repeating, repeating, moving ahead... repeating, repeating... moving ahead and it will appear to "automatically" program, however, YOU HAVE TO DO THE WORK, for it to work. Which you are, and I hope even enjoying it? NOW is a great time to find CONVERSATION opportunities around you. Don't be shy, go find some people to practice your English with!