I just finished The Italian Secretary by Caleb Carr, a "further adventure" of Sherlock Holmes.

It's a pretty good Holmes story, involving Scottish nationalists, a hoax ghost (or is it real?) and some medieval siege equipment. The beginning and middle, where the atmosphere is developed and it is carried by Holmes and Watson's interactions, are stronger than the end, which is dominated by action sequences and less interesting conclusions.

One minor complaint - why do writers who want to do a new Sherlock Holmes story insist on throwing in references to the other stories, something that does not occur regularly in the Canon? It's a weird form of name dropping that doesn't really serve a purpose - we're already reading a Sherlock Holmes story - we don't need to be reminded of other ones, particularly given the fact that since they are the originals they are probably better than the story we are reading!

For some reason while reading this book I had the uncanny feeling that I had read parts of it before, while parts seemed new. The afterword mentions that it was originally a novella so it's possible I read that in a collection at some point.