Sonata by Juan Tamariz, but a better English translation and keep the dust cover art because it's beautiful. Even though I own a copy myself, I'd love to have one with better translation!
Technically not out of print to my knowledge but I need the English translation of The Magic Rainbow by Tamariz. Only in Spanish right now, and it's killing me that it isn't in English yet.
A new printing of The Books of Wonder is something that I wish would happen.
Would also love to get my hands on Andy Nyman's Bulletproof. I think after those books I think my collection would be pretty much set and I would never want to buy another book again until something great comes along for the collection. One can only hope though!