The Devil in the White City - would love to see the Chicago Worlds Fair brought to life in all it's splendor, and to be directly contrasted with the horror that was HH Holmes murder castle. The book brought that history to life so vividly, and I feel like mini series with great casting would do incredibly well.
The 7 1/2 Deaths of Evelyn Hardcastle - mysteries and whodunnits are popular again (thank god) and this one has such an interesting premise. When I first read it I was convinced it would be a great video game. But a movie would also be a hit.
Something Wicked this way Comes - not sure if this has ever been adapted, but I've never seen it. The book is so atmospheric and has such a rich cast of characters. We haven't had a movie that really celebrates the moodiness of autumn in a while.