This book was a mixed bag for me. On the one hand, it is exceptionally well researched, with lots of little information that I haven't seen elsewhere. On the other hand, while Wescott goes to great lengths to state over and over and over that he only follows the facts, he then makes gigantic assumptions anyway. He engages in rather astonishing logic gymnastics in order to create possible scenarios, as if viewing himself as some sort of modern day true-to-life Sherlock Holmes.
But I suppose, for me, the aspect of the book that drags its rating down is Wescott's relentless tendency to dismiss virtually all other Ripper authors with words like "meaning no disrespect to author X, who wrote a book on the Ripper", which he immediately follows with derisive hyperbole, reserving tiny bits of praise only for those whose work doesn't clearly overlap his. In other words, he has staked out his turf, and anyone who encroaches on it gets an elbow to the face.
It is a shame that Wescott's titanic ego mars such well researched material. Nonetheless, I can still recommend this book, because it has great information, and some of Wescott's conclusions are actually pretty fascinating.