I think a reader's enjoyment of this book can be measured by whether they can believe the central conceit. Holmes meets young girl and makes her his partner. In all honesty, I'm not sure I believed it. Mainly because there is a strong sensation that the author is just writing her own fantasy, the other and this is more interesting, how much of what Mary Russell tells us, can we believe? She constantly tells us that Dr Watson's accounts of Holmes are not accurate and inclined to being made more fantastic, so as a reader are we supposed to apply the same scepticism to Mary's account of events. It does add subtext to the novel, having an unreliable narrator. Note, also her attitude towards Watson. Her reading of Watson as an idiot that she and Holmes are rather condescending to smacks more of Mary's jealousy of the friendship between them. Anyway enough of that, the mystery itself is not that strong, at the end of the day, there isn't that much to work out. A fair read which I did enjoy but wasn't that convinced by.