I complained about this elsewhere, but I really wish they'd release the Halo art books (making off, Warfleet, Mythos, etc.) as digital books at some point. I don't have room for more stuff, let alone Halo stuff, so basically I can't justify buying them if they're gonna' take up room. Especially for referencing in articles and the like, the digital copies of the books are much more useful as well.
On a side note, I'm somewhat annoyed that Gears of War 4's digital art book doesn't support the kindle reader on iPad. Such a bizarre omission, but oh well. Money saved.