Math Smart Junior, 2nd Edition (Smart Juniors Grades 6 to 8)

This book offers a range of middle-school math concepts, explained in story format. The story is age-appropriate, and although it's rather lame and strains in places to be funny (the giant talking animals are a bit much) it is actually fairly effective.

Almost the second half of the book is devoted to elementary school math as a review section, and I appreciated that they put that later in the book than the harder stuff: a student who is not doing so well in math is not going to be greatly cheered by a book that starts with "2+2=4 and why". By putting the review at the end, it can be read and digested at the student's own pace, instead of the pace of the book.

I am using the book for a slightly younger student who is struggling with math, and he is having fun with the scenarios that the story offers. However, I am guiding him through the problems and explanations: grades 6-8 is probably right on target for a student working independently.