This has been an excellent, incremental way to teach my daughter her addition and subtraction facts (as well as to review a few other things, such as less than, greater than, basic money facts, word problem phrasing, etc.). These books can easily be used WITHOUT the teacher's guide, so save your money and just get the workbooks without that guide, and jump right into them. (There are a handful of workbook pages that will be senseless without the guide - just skip those.) There is so much practice on the same stuff that mastery seems almost inevitable. In fact, there's so much practice that, depending on your student, you may find yourself judging that you can skip a workbook page here and there. But I like that the practice is AVAILABLE. And I like that there is opportunity to reinforce the information until it's grasped. I tended to just circle problems I wanted my daughter to work on and tell her to skip the rest, and sometimes we'd skip entire sheets, but I definitely feel this repeat practice has helped her to get the facts deep down in her head for quicker recall. I like the way it systematically builds. But do be flexible and be willing to skip when it’s clear the student has gained mastery, otherwise it can turn into the sheer drudgery of busy work.