Finished reading The Whole Truth by Philip Mackie. The play is a 1955 English murder play with a plot that keeps you guessing. I recommend it highly for its clever plotting and suspense.
It was also made into a movie. I have the impression that the movie plot was reworked, and may not have come out as well.
I took it out of our public library, which has a bunch of copies. Otherwise, it looks like it's a rare and expensive book in the US. But you can get one cheaper if you order from the UK.
But some some savings will be lost
in increased shipping cost.