I remember starting with book 1 as a child. My teacher had me go through all the book levels. As an adult who is picking back up her violin after about 6 years of not playing, I found going back to book 1 and working my through the levels again to be a great reminder. It helps you to build up proper technique and intonation. I typically spend about 30 minutes on technique work an then about an hour to an hour and a half on actual pieces.