There are any number of books based upon the Conan Doyle stories but I've become hooked this summer on Laurie R. King's Mary Russell and Sherlock Holmes mysteries.
Ms. King decided that upon his retirement to Dorset, Sherlock befriended a promising young American girl who as she matured became Holmes' intellectual equal. Over time the fell in love and married, taking on cases only as necessary.
Holmes and his brother Mycroft are portrayed more humanly than Doyle ever let on, and although purists may choke on the suggestion that Sherlock wed, Russell is a more perfect foil than Watson.
I'm 4 down with the next 2 on order from my local bibliotech. I give them a B+.