Although this workbook is not necessary to complete the course, it keeps all the student's work in one place. This is advantageous for test review. Furthermore, only one item needs to be kept as a student record for completing the course. I think it is worthwhile if your budget allows for the convenience.
This notebook is awesome. I wish I had gotten this notebook 2 years ago when my oldest daughter studied this course. The pages are bright and beautiful. The clearly marked daily plan at the front of the book takes away all the planning and guess work. My child knows exactly what she needs to do each day to complete the course in a timely fashion. I love having the Study guide pages, and experiment recording sheets right there inside one notebook. The only thing I wish the notebook included was the tests. As it is now, tests are only found in the Test & Solutions booklet and they must be printed out. It would have been great to keep everything in one place. (or include a folder pocket inside the notebook cover to store the tests)
My son is only 1 module into this text (there are 16 total), but so far, it's just fine. It gives him places to write & record everything that the hardcover text requires, such as experiments. Also, I like that there is a study guide at the end of each module AND a summary -- both of which can be used to study for the test. (The answers to both are in the text/solutions book.) I'm glad we bought this as a companion text to the hardcover and will put it to use, for certain.
I ordered this notebook to make it easier for my son to work independently and have all of his written work, including the lab write-ups, all in one place. I love that it includes an easy to follow schedule with each day's assignment so that he can check them off as he goes through the curriculum. Unless I've missed something, the only thing it doesn't include are the test pages!