This guide covers a lot of the security problems associated to web applications and guides in how o review code to determine security failures. I do wish this guide were longer and a bit more in depth. Considering that it is a freely available document on the web, the authors could have gone a bit more into each problem (explaining the problem). They probably considered it out of the scope of the book or that OWASP already has other docs referring to that in depth analysis. Still, this being the first doc read from OWASP, some of the examples left me unsure of what the problem was.
Still, It is worth a read and an excellent starting point to setting up review checklists for code reviews.