Knowing how GW is doing business, any new book (digital or not) will have to be bought again.
Digital versions being the same price as a printed one i would advise against it since i consider that to be a big rip-off.
Furthermore, even though i love the models, the game, etc. I would encourage buying from independent webshop retailers. Its usually sold at 10-20% discount compared to GW standard price.
Especially since GW's new policy of NOT having any stocking in their own shops. They only have some core and some topsellers for sale and all the rest needs to be ordered from the webshop.... at the same price.
So you order something (shippingfree) from a webshop, need to wait a week and u pay the same amount as you would in the shop itself, i find that to be utterly client-unfriendly and outright unacceptable.
I bought 90% of my 5000+ army through online independent retailers (GW still makes a profit on it) and ebaylike websites that sell used stuff. definately spent less than 60% compared to GW prices. which is clearly 400 euros less.... if not more.
IMO GW is overpricing thanks to shareholder profit-hungriness, combine it with the GW-policy of being aimed at pulling in new gamers/hobbyists. They care nothing for people already in the hobby.
Shareholders want big profit margins and that skyrockets prices and makes for consumer-unfriendly policy.