I read cozy and historical mysteries, a bit of Paranormal/UF, and to mix it up, I read science and gardening books on occasion.
That half star is because my expectations, based on previous Heyer mysteries, were completely blown away.
Envious Casca is both a text-book Country House Mystery and Locked Room Mystery, and it's far and away the best Heyer mystery I've read so far. It's a slow burn, certainly; almost half the book goes by before anyone dies, but Heyer placates her audience - at least this one - with the acerbic humour and no-holds-barred verbal warfare that takes place amongst the family members, written brilliantly by Heyer. These people are so vile to each other the only wonder is that the blades didn't come out sooner; at one point, tea was served and I thought to myself "I wouldn't drink that if I were you. Any of you."
It feels like it would be too easy to give away important plot points here, so I'll just say the murderer wasn't who I thought it would be (although I was close), some of the characters were a little too vile to be believed, and I'd have preferred at least one more paragraph, preferably a page, at the end. There's a small romance, because it's Heyer, but I'm not sure it isn't launched and HEA'd all on the same page, so it's really not more than a small also-ran. That it would end the way it did felt inevitable, but there was never any actual romancing.
The more I type, the closer I get to spoilers, so just read it if you like anything you've ever read by Heyer (she's hit and miss in both romance and mystery) and you're in the mood for a slow read with great, biting dialogue. I don't think you'll be disappointed.
I read this for Halloween Bingo's Country House Mystery square.