There is a Casual Optimist Tumblr as you know, but I don’t post a lot of new book covers there. Fortunately there are other Tumblrs that do focus on book cover design if that’s your thing. Here are a few that I follow:
Book Covrs (pictured above: Trying Not To Try by Edward Slingerland; design by Gray318)
Booketing (pictured above: One Last Thing Before I Go by Jonathan Tropper; design by Jim Tierney)
CMYK / Vintage Books (pictured above: The Country of Ice Cream Star by Sandra Newman; design by Julia Connolly)
HarperCollins Design (pictured above: Treachery by S. J. Parris; design by Alexandra Allden, illustration by Daren Newman)
Penguin Design (Pictured above: The Moon is Down by John Steinbeck; design by Jim Stoddart)
Random House Art Department (pictured above: In Cold Blood by Truman Capote; design by Eric White)
Verso Covers (pictured above: The Oil Road by James Marriott and Mike Mino-Paluello; design by Alex Merto)
There are also several book designers who are on Tumblr in their own right. Here are some that use it showcase their work: Robin Bilardello, David Gee, Kimberly Glyder, Greg Heinimann, James Paul Jones, Oliver Munday, and Stephanie Ross. (Pictured above: The Tin Horse by Janice Steinberg; design by Kimberly Glyder)
Who am I missing? Let me know what book design Tumblrs you follow!
(Pictured top: The Quick by Lauren Owen, illustration by Jim Kay, taken from Vintage UK’s CMYK Tumblr)
Update:
Two I missed…
Hey, Good Bookin’ (pictured above: Wolf in White Van by John Darnielle; design by Timothy Goodman)
Lovely Bookcovers (pictured above: Evening is the Whole Day by Preeta Samarasan; design by Leo Nickolls)