In the Still of the Night - Jill Churchill
This is the next book in the series after Anything Goes and, like the previous book, it features Lily and Robert Brewster, a brother and sister who have inherited a large house in the middle of the Great Depression, but not the money to keep it going and live in the style to which they used to be accustomed.

This time around, they hit on the idea of trying to make some cash by inviting well-known people to stay and then getting other people to pay to spend the weekend with them. After a couple of disappointments, the Brewsters manage to snag the services of a bad-tempered writer whose books draw strongly on the horrors of the Great War - their scheme seems to be paying off, till one of the guests is found dead and then another disappears.

In the Still of the Night is another well-written story that makes you want to know what's going on, and though I figured out some of the overall mystery from the hints that are dropped quite early on, it's not as clear-cut as all that. The series continues in Someone to Watch Over Me, for which I shall be keeping an eye out.