After becoming engrossed by the imagery of the cover for Scott Lynch's Lies of Locke Lamora, I decided to do some digging for books that I would buy simply because of their covers. There are a lot of interesting pictures for Science Fiction and Fantasy covers, but many of them are forgettable, confused, or simply boring. To my mind, this is a really terrible artistic loss, or loss of artistic opportunity, since I would imagine of all the readers, Science Fiction and Fantasy audiences are in the most ideal position to fully appreciate imaginative cover art. The few titles I have listed here are by no means exhaustive, but range from the comic (Sense and Sensibility and Sea Monsters) to the pensive (Lies of Locke Lamora).
I was hoping to find some really potent, high fantasy covers, but the closest I could find was Robert Jordan's Wheel of Time series. To my dismay, many of the genuinely fantastic covers from the Dragonlance series that I read as a child have been reissued with new, less exciting (less fantastic) covers.
Sense and Sensibility and Sea Monsters
Jane Slayre
The Lies of Locke Lamora
Before They Are Hanged (The First Law: Book Two)
Lamentation
Canticle (The Psalms of Isaak)
The Dragon Reborn: Book Three of 'The Wheel of Time'
Crossroads of Twilight (Wheel of Time, Book 10)
The Eye of the World (The Wheel of Time, Book 1)