This is a general, "what books have themes or content that would make for great movies" question. Graphic novels are included here.

Could have posted in ~talk or ~movies, but I'm seeking the opinions of dedicated readers, who've had the thought in considering a story, "I'd really like to see the visuals for this", or "a movie/series adaptation could expand on these themes".

Also, what were your biggest disappointments in the rendering of a book into a movie/TV series?

My picks:
Ursula Le Guin, The Dispossessed. Can't say that it's likely to get the nuanced treatment it deserves, but an even-handed visualization of socialist vs. capitalist societies is overdue, and it's got spaceflight and FTL information transfer.
Warren Ellis, Transmetropolitan. Not that he's ever going to grant the rights, but this one's a no-brainer for American cinema - brash, loud, splashy, violent, with bigger-than-life characters and themes.
James Tiptree, Jr. (a/k/a Alice Sheldon), Her Smoke Rose Up Forever. I'd love to see a short series based on this collection.
China Mieville - anything from the New Crobuzon books. The baroque ruin backgrounding the scenes, and the panoply of characters, should make for amazing cinema; a little judicious editing will be needed to make the stories work for the screen.
[Obscure] Norman Spinrad's Bug Jack Barron, subject to timely and relevant updates for 21st Century media. There's a great theme about how selective presentation of video clips and the editor's viewpoint influences the story being told.
K.W. Jeter, Farewell Horizontal, this one's gonna have great visuals, trust me.
John Steinbeck's The Grapes of Wrath, remade as a story about border migration.
Joe Haldeman, The Forever War - man, is it ever time for this one in the U.S.
Dan Simmons, Hyperion - the World Tree, the Shrike, and plenty of other opportunities for fine visuals.
Salman Rushdie, Haroun and the Sea of Stories. Another candidate for an anthology series; perfect for animation.
Tibor Fischer, The Thought Gang - it's a heist story, but also a comedy and a satire. Kind of amazed no one has made it into a movie before.

Biggest recent disappointment - The adaptation of Richard Morgan's Altered Carbon. Edited to completely discard the political messaging and amplify the sex/violence. Turgid, poor special effects, and gruesome acting.