The Italian Secretary features a sadly anemic Watson's pitifully anemic account of how a dreadfully anemic Holmes solves the horribly anemic "case" of the haunting of Holyroodhouse. It was preposterous from the moment Holmes and Watson are called to Scotland by Mycroft, who is apparently on very intimate terms with Queen Victoria. Like is said, preposterous, not to mention sadly underdeveloped. Instead of building the case throughout the narrative, Carr simply insists at every possible juncture that everything that happens is either breathtakingly thrilling, important or dangerous. It is not, though clearly the reader is meant to think otherwise.
Carr is obviously a genuine fan of Arthur Conan Doyle's (I can't fault his enthusiasm - I'm a huge fan myself), and he's clearly read the canon. Unfortunately, this obvious knowledge and appreciation did not translate into a compelling "further adventure," or even a convincing portrayal of the master detective (for that go straight to said canon, or the Granada TV series with Jeremy Brett). Rather, The Italian Secretary simply made me feel cranky and dissatisfied - a feeling that only went away after I'd re-read "The Blue Carbuncle" and "The Resident Patient." So that's what I would suggest - stick to the real Adventures of Sherlock Holmes (or any of the other canonical collections or novels) wherein the cases and the hero are anything but anemic.