We have the Word Roots CD-ROM, which I LOVE, LOVE, LOVE. It gives the boys something on the computer, which they crave and we limit, and it grades for me.
It REALLY did improve our oldest son’s vocabulary and writing and though he didn’t love it, I saw proven results. I will be ordering the next level for him to complete in the fall.
With both the CD-Roms and books, they are NON-consumable, which is a big + if you will be using with multiple children.
I do recommend the Word Roots, but we used the CD-Rom (I think the book is much the same). If your child doesn’t love workbooks, the CD-Roms might be an alternative.