The Santa Klaus Murder by Mavis Hay

I heard about this story on the Classic Mysteries podcast and was delighted to see it was available on NetGalley. Like many of the books from this time period, it took me awhile to wade through the story, even though the premise hits a lot of my catnips.
Old English country house (check), set at Christmas (check), money-hoarding patriarch (check), family that's resentful (check). What's not to love? And I just can't put my finger on why it took me so long to finish this book. Part of it was the varying POVs. It got a bit confusing in the beginning. Especially with so many characters.
All of Sir Osmond's children have some reason to resent him. Whether it's his daughters who are threatened with marrying "suitable" men or being cut off or his sons who can't break free from his reins. Then there's the pretty new secretary and the fact that Sir Osmond is threatening to change his will. What was it that drove someone to dress up like Santa Klaus, hand out some gifts to the children, and then shoot Sir Osmond?
An intriguing mystery, especially if you like 1930s English cozies, but, again, can be plodding in points.