As far as math textbooks go, this is clear and understandable. The author describes real and mostly practical applications, so you're not learning anything without reason. The simple language makes me feel like relearning this stuff is no big deal, though I'm about 12 years rusty.
HOWEVER. This book is riddled with typos, which is a shame for someone like me without a lot of math confidence. Also, the very light gray text describing steps in a problem is hard to read. I think this was originally designed in color and printed in black and white without any followup check.
So, basically, proofreading. This math book needs proofreading.