Any José González, I listened to loads in the summer revising for exams, and it just made me relax. Any jack johnson really is relaxing, expect for some stuff off his first album, that can make you rather depressed to be honest.
If it's for reading, look for anything that you don't [i]have[/i] to think about. That, for me, means no abrupt tempo changes, no lyrics, etc. Post-rock is decent, though it's getting be so ultra boring for me. Ideally, you don't want to throw your money at something that's going to bore you to tears when you're not reading. Something that isn't [i]just[/i] background noise.
I'd suggest checking out some minimalist stuff such as Lubomyr Melnyk or Terry Riley. Steve Reich - Music for 18 Musicians is pretty good for that too. It's all easy to turn off and they don't sound particularly complex on the surface, but there's [i]so much[/i] going on when you start to dig.
If you want something that isn't as obscure or weird (because, from your list, you don't come off as an avant-garde kind of duder) The Mercury Program or Tristeza may work for you.
Of course, there's a whole crap load of awesome ambient that would work perfectly for this too (Eno's Ambient 1: Music for Airports for starters).
Stuff to check out:
Wave-LoxRainbow in Curved AirMusic for 18 MusiciansA Data Learn the LanguageA Colores
Hope that works.