The first thing to realize is that while short selling is pretty much the opposite of going long from a mechanical point of view, the short seller's mindset cannot be simply the opposite of that of a buyer. This is because there are a number of key differences between going short and going long that force the short seller to alter his approach. Some of these differences include interest payments (because shorts have to borrow shares from those who own them), timing (the lender can call these shares back), and the return profile (a stock can rise infinitely, vs a long, whose maximum loss is what he paid for a stock).
Kumar discusses these and other factors and how they influence what constitutes a good short candidate. Demonstrative case studies can be found throughout the book, helping illustrate why certain heavy shorts ended up going right for short sellers, and why others went wrong. Some of the insights offered are similar to those provided in only the most sophisticated investing blogs and stock investing forums.
I found the book helpful, particularly the case studies, to better understand what a short seller needs to have happen in order to be right. Enjoy!