Both my younger kids are using the same year (Grade 6) and I bought the book but planned on not using it (bought the package used, book never used) and figured I could resell it all again. However my 10 year old was having a hard time doing the program on the computer because he had to write out all the problems on paper and it was just too much to do that, make sure it was lined up and do the problem. So I switched to the book and it made a huge difference.
So, no you don't need the book unless you have a child that might have that problem.