Not sure what to think of this, am sure will come to android eventually. A lot of companies produce content for iPad or android first, and then roll it out to other platforms later. The thing that gets me is that if you already own the codex you have to pay £25 for the digital version.
I don't play, but paint the miniatures and read the fluff like it's going out of fashion. I have all the current codices and a number of the older now defunct ones, you should be able to take your copy into the store and request a voucher that gives you the right to buy for 2.99 or something. They look great, just not sure at all that the price is worth the 'extra content'. Handy for FAQ and new unit updates, am assuming they could be updated like an app update?
I only generally buy paper books, and I still buy CD's. I wouldn't buy the mp3 version if I already have the album...