You are considering whether to buy a product. You look at the reviews. Would the following review decrease or increase the chances of you buying the product?
Review title: far too many errors to be truly useful
Product review: If the purpose of instructional books is to build a foundation of knowledge in a subject, this one fails. The concepts are presented in a relatively straightforward fashion, but there really aren't enough problems to enable the reader to master those concepts. As many other reviewers have noted, the book is riddled with errors, including some arithmetic errors that are so painfully basic that the authors should be embarrassed to have their names attached to the finished product - and those are just the ones I noticed; I'm sure someone who really knows their precalculus could find dozens more. If I wasn't already fairly comfortable with math, the errors in this book would seriously undermine my confidence in my skills; as it is, they just undermine my confidence in the authors' skills.
