This is the only mystery series that I like reading out of order. And it actually does make a difference! In that, things happen in previous novels I haven't read yet that pertain to the novel I'm currently reading. For some reason, this doesn't ever bother me. So, I've read books #1, 2, 3, 5, 6, 7, 8 and 10. (Thankfully, I'm now only missing two in the middle there.)
I find King's pretense of Sherlock Holmes being real (the fiction of him being real, which is fun thing number one) and him being married (to a much younger woman, which is fun thing number two) completely engaging. In a lesser author's hands, this would be the mightiest failure. I can imagine her agent quailing at hearing about this new series - "wait, you have a successful series about a lesbian detective with a background in theology, and now you want to mess with one of the classics - are you nuts?!"
Well, read it to believe it. She pulls these stories out of what seems like thin air, all the while giving them a realistic enough turn to make the 1910s feel like you're reading about today. Except for the Victorian-style language (and the plot settings), this would be entirely true. This particular story is about the 1906 San Francisco earthquake, and the ensuing fire and general mayhem. Plus it has a personal bent (ie, the mystery plot hinges on one of our main character's past), which makes us care more for the outcome.
Also, Sherlock and Mycroft like each other in this series. As opposed to what I consider the overwrought family dynamics of the British TV series.