Dorothy Sayers' Clouds of Witness
The second Lord Peter Wimsey finds his older brother, the Duke, arrested for murder! And the dead man is their younger sister's fiance! And she's definitely keeping some secrets too. Sayers definitely kept me guessing with this one--there are soooo many clues and red herrings--but it totally all makes sense in the end and is abundantly satisfying. I did wish the lawyer's speech at the end was slightly less lengthy, but that's a minor complaint. I really find these books so calming, though maybe that is weird to say about a murder mystery. A-.