Runic wrote:
I recall that the Space Wolves Codex: Wulfen Edition includes all the stuff from the Wulfen book. I might be mistaken about the "all" part though, might want to check on that.

I'd say that is your best bet, as it includes the normal rules in addition to the new formations. Almost everything you can have.

 SharkoutofWata wrote:
If you're getting something digital, why not get it all? You don't need a single physical book to play 40k. Digital is just as allowed by GW, or else they wouldn't sell them. No need to clutter the table with outdated books and more importantly, no need to waste money buying the old version AND the new version.

But Champions of Fenris is a very good alternate way of building a Wolf army. For most people I've encountered, it's the 'only' way to build Space Wolves.

 Runic wrote:
I find it unfathomable that playing at a GW store would be prohibited when using a purchased digital copy. Their own product. If that's what you were worried about.

If you're talking anywhere else, then I recall even the largest tournaments around allow digital devices. To my knowledge it's quite common practice.