The Dorling Kindersley _Math Made Easy_ workbook series is one of the better investments the DadsWorksheets.com family has made. Each book in the series contains just over 150 pages of exercises tailored to grade-appropriate knowledge levels. We've worked through three of the series here and as we move up grade levels, these books are definitely one of the core resources at home. The problem density in these books is very high. Several other books we've used have only six or eight problems per page, with a lot of margin fluff. While some of the problem pages that require illustrations or charts may be light on the problem count, most of the pages in the DK series have substantial number of actual exercises. Coupled with the high page count, you really get your money's worth.
The content covers a wide and useful range of topics, and its reinforced as you move from book to book in the series. Apart from basic operations the series covers chart reading, money, fractions, measurement, symmetry, geometry, word problems and more. A complete answer key is included in the back of the book. The topics are repeated within each book, which means working cover-to-cover isn't repetitive... There's no getting stuck in a chapter that focuses on a narrow set of topics. You'll appreciate having a change of pace the first time one of your kids works through a page full of problems somewhere.
The worksheets themselves are fairly plain and printed using a two-color process (blue and black.) Some friendly illustrations adorn most pages, but you wouldn't characterize these as colorful or verly engaging visually. The focus here seems to be on the actual math, which suits Dad just fine here. The books come with a set of gold stars that can be used to mark off the pages as they're completed or graded (Your mileage may vary. iTunes credit worked better as rewards here.)
The book is printed on a stout paper stock, and is put together with a sturdy stitched signature binding. You won't be tearing any pages out of these volumes, either accidentally or by intent. The paper is slightly slick and holds up extraordinarily well under erasure. After suffering with a pile of newsprint-type workbooks, I'm amazed that someone seems to have put so much thought into the production quality of these books. Some of the $50 books I use professionally aren't this well put together.
Overall, the Dorling Kindersley _Math Made Easy_ books are worthy of Dad's highest recommendation.