On the one hand, this was a distinctive take on the average Holmes pastiche, where the POVs of Mann's original characters are interspersed between Watson's first person narrative. Instead of a client bringing the case before Holmes in the usual manner, we are given a firsthand account of what occurred from the other players. It deviates from my taste in more conventional pastiches, but the side characters were so well drawn they take on a life of their own, and become just as much a part of the book as Holmes & Watson. Two separate plots also come into play - the clues are strewn about where we cannot see them, but of course, Holmes can, and I thought the unfolding of the actual mysteries were one of this book's strengths.
Yet, for all that, I would have to say my technical rating would be 3.5 stars. What ultimately happened is that the multiple viewpoints may have been used too frequently, creating an excess of unnecessary detail, slowing the pacing in many instances or dampening the suspense when things should have been at their most exciting. And it might just be me being an insufferable nitpicker, but there were times I felt he had the doctor and detective spot on, while other instances they were just cardboard Victorian cutouts.
Overall though, while not this author's best work, in my opinion its strengths outweighed any shortcomings, and is one that deserves to be counted among some of the better pastiches out there. Aside from the instances of plodding pace, I cannot see this as being a disappointment to anyone who likes to get caught up in a good mystery.