Just Make Believe by Maggie Robinson

Addie is at a house party when her somewhat-less-gone-than-he-should-be husband, Rupert, appears. Luckily it is just as she's being thrown by a horse. Unluckily, it's because there is trouble heading her way.
The host and hostess, Hugh and Pamela, have a decent marriage, but his lungs were damaged in the war and he has a bullet lodged in his spine. Small wonder, then, that there are rumors flying about his wife having an affair with a much older man, a landscape designer, Simon Davies. Also present are three of Hugh's friends from the war and some young ladies.
Rupert's prediction comes true and there is a death, the lady of the house, Pamela. But then another body, that of a young soldier turns up in the garden.
The whole thing ends up being very convoluted but still a good story.

Three and a half stars
Follows Who's Sorry Now
Borrowed this book from the library
Opinions are my own