Any Shape or Form by Elizabeth Daly

Henry Gamadge has been invited to a party next door. He's maybe not particularly interested but his cousin encourages him to go. And it is there that he meets a colorful cast of characters. He knows the Drummonds, nearby neighbors but the young Malcolm siblings are unknown to him. And they are equally unknown to his neighbor's aunt, even though she was their step aunt. And there is the added complication that their father left his money to her for the extent of her lifetime. So they are potentially wealthy, but only on expectations. Until then, they live off Vega's largess and the allowance their father left them. 
Vega herself is a colorful lady. Her name has only recently been chosen as she has joined a cult that worships the sun. She even gifted the home owner, her nephew Johnny, with a sculpture that was possibly originally Apollo but now is rather faded and missing whatever it once held. 
There are undercurrents all around the party but Gamadge doesn't expect Vega to be shot, while he's standing next to her in the garden no less. The perpetrator could have been anyone as they had all split up previously. 
An unexpected guest shows up and then she is also murdered. The police are looking at the wrong person and it will be up to Gamadge to set them right.
I am not sure that this was really a fairly clued story but it was a good one. Recommended by Classic Mysteries podcast.

Four stars

This book came out in 1945

Follows The Book of the Dead

Followed by Somewhere in the House

Kindle ebook

Opinions are my own