I came across a quote from Robertson Davies the other day which sums up perfectly my feeling about Cullen, as about several other true crime writers: "She was worse than a blabber; she was a hinter. It gave her pleasure to rouse speculation about dangerous things." This is Cullen in a nutshell. He hints, and it drives me crazy. He goes about ninety percent of the way to outlining a case that Ethel LeNeve was the actual murderer--or at the very least Lady Macbeth to Crippen's dithering--but he never comes out and says it. He keep leaving it in implications and hints, without even the decency to put it out there as frank speculation.
The book has other flaws, particularly in the hard to follow, chronologically higgledy-piggledy structure which Cullen clearly chose as providing maximum drama rather than maximum clarity. But it was interesting, if for no other reason than that it demonstrated a man could be a brutally cold-blooded murderer (unless that was Ethel), could immolate himself in self-sacrifice (even if Crippen committed the murder alone, Ethel clearly was an accessory both before and after the fact, and Crippen was willing to tell all the lies it took to get her acquitted and himself executed), and could still be banally sentimental, intellectually and ethiclly muddled, and--except for the fact of his uncharacteristic crime--utterly uninteresting.
The book also confirmed my belief that Walter Dew is not a trustworthy source for anything, and Ripperologists need to stop quoting him.
It was a struggle to finish this book. Cullen took an interesting, at times gripping, story and made it plod along. I agree with another reviewer who said it would be nice if the author had put forth his own speculations about how the crime took place, obviously he spent a significant amount of time researching the matter. 2.5 stars would be more appropriate.