Hollow Crown / Dangerous Sea, David Roberts
Sweet Poison and Bones of the Buried.) His series about Lord Edward Corinth and Verity Browne definitely improves as it goes on. While I still have certain reservations about the books (In particular, when I initially started reading the series I was concerned that Corinth and Browne would simply be a less literary Wimsey and Vane, usually there's at least one character who, if not a real historical figure, is clearly meant to remind the reader of one, and there's always a degree of scene setting), I enjoy them nonetheless.
There are two main things that I appreciate about this series: first, that there's not always an unmasking of an individual with a dastardly plan behind the deaths in the books. Sometimes the death is simply an accident, sometimes a killer can't be brought to justice. It makes the stories feel more realistic. Second is the politics. I don't know whether Roberts had all ten novels in the series planned when he started writing, but all the novels engage with the turbulent times leading up to the Second World War, and characters often have very different viewpoints. Moreover, like real people their views change as history unfolds.
In Hollow Crown, it's Autumn 1936 and Edward is given the task of retrieving letters stolen from Wallis Simpson – letters sent to her by her lover. (You know who!) Unfortunately the woman who took them, a former mistress of the Prince of Wales, is killed and the letters disappear. Dangerous Sea is set in Spring 1937 and mostly takes place on the newly-launched Queen Mary; having proved himself useful, Edward's contacts at the Foreign Office want him to accompany a well-known economist on board the ship and make sure he reaches America, and an important meeting with President Roosevelt, in one piece.
Enjoyable fluff for rainy afternoons! (And we've certainly had enough of those of late.)
Source of books: One of these was bought from the Oxfam bookshop; the other doesn't have a sticker on so I'm not sure where I bought it, but it's definitely secondhand.