The CD is a must if you order the books, volumes 1 & 2, and I do suggest you get them and this CD.
As others have stated, the CD is piano and cello playing the pieces from the books; you play along. Although I have an excellent teacher, as a beginner practicing on my own, I could never tell precisely where the correct intonation (note) is; one millimeter off is not the note, and I was feeling quite frustrated.
If you are struggling with finding the exact proper pitch, this system will help immensely. I don't know what the Suzuki method is per se, but I do know that playing with accompaniment is crucial to developing intonation, plus you learn to keep time, employ the dynamics, etc. I work on the things my teacher assigns, and I also use these Suzuki pieces, usually as warm-up. I like that I am getting a lot of exercise for my 3rd and 4th fingers, which are relatively weak, I like that I am learning to keep time. Highly recommended if you are a beginner or can't find the notes exactly just yet. If you can find the notes exactly, this system would be of limited use in my opinion. For me, at this point, it is just what I needed.