Hi Kaspar, there is actually a paperback version of Andrew Stephen's book. I have a 1988 edition. You may be alluding to it being difficult to find.
The AS book would be the essential starting point for anyone investigating this case, including DV himself, as there's no other definitive version and AS had very good cooperation from detectives working on the case. DV makes no reference (that I can remember) to the AS book despite making frequent mentions of press and less direct historic material.
Significantly, AS flatly contradicts the central thesis in the later DV book, that detectives never searched 37 Shorrolds Rd on the night in question. Contrast pp10 of AS with pages 115-116 in DV: Kindle version ). The DV passage imo is highly erroneous and I suspect deliberate. It does of course destroy his central thesis so you can see why he muddles and fudges over it. Not making an immediate search of premises where someone could possibly be lying dead inside or badly injured, defies basic common sense as well as fundamental principles of policing. DV lamely quotes one of the CID officers he speak to, as not remembering if anyone went to Shorrolds Rd or assuming the Sturgis manager had gone there instead of the police - a likely story! AS by contrast, states that not only was the place immediately ordered to be searched, the duty inspector, Johnstone, who rushed in, also went to Shorrolds later that night to see for himself. The key then becomes the next fudge as DV tries to draw his reader in to the conjectured bollox he conjures up over the other side of the Thames.