This is one of two review supports I purchased recently for my daughter. Math is the boogey monster under her bed, so to speak, I think she may even like spiders more then math, and those she's only find of one variety- the dead kind. And I noticed at the beginning of the year that she could use some additional supports and reviews for the previous year's math concepts. My rating of this is based on the product being marketed as a workbook, which is what it is most appropriate for. If you are looking for a comprehensive curriculum, meaning includes text book level explanations, I would recommend actually ordering from Singapore Math directly. They also have teaching manuals that explain the concepts to you and how to teach them to your kiddo. I used those when I was home schooling our daughter during her third grade year. This is a workbook produced by a separate company only with a brief review of the concepts that is based on the manner of instruction developed by Singapore Math, Inc.
As such, I did look this over. There is a bit of an overview of some of the methods Singapore math uses. I know that when I was in elementary school back in the '80's, things were taught a bit differently then they are now, and I know for many of the common core states, they have adopted methods and standards that draw on Singapore Math's methodology, so...as tempting as it is to teach your kiddo the way you were taught growing up, they will be tested on knowing how to do it this way, so, I think it is helpful they do have an overview. However, since it is just an overview, as this is only intended to be a support workbook, you may find yourself combing you tube videos for expanded explanations if you don't already have text book resources that go over this for you or your kiddo.
There is also an example of how to solve the problems being done at the beginning of each of the unit sections. Now, I know my girl, and I know she's going to find the lack of illustrations in this to be boring as heck and would say it borders on the dreadfully dull. However, I think the worksheets are put together well, and I love that there is enough space given to do the work on the page without requiring a separate scrap page. And, since she and math aren't so very fond of each other, probably the only thing she likes about any math book is cute illustrations, and I'm rather of the opinion that this is not the most important feature of a workbook by the time you get to be her age. Especially since if they're too cute they're super distracting, so I am not taking off for the lack of happy inducing illustrations.
So since the necessary elements of 4th grade math have worksheets (over 200 pages worth), there is an answer section at the end, there is a brief overview in the beginning, examples at the beginning of the units, adequate space for completing the problems...I am saying that this is a 5 star workbook. I don't think this should be used as a stand alone homeschool curriculum, but I do think this could be a good support for that or a good practice book or review book for a kiddo who's already been through the instruction and just needs a bit of touching up on their skills.