I'm enjoying it, and I've not wanted anything to do with the 40k universe for ages.
As Gary says, just the book and you'll be doing fine (there's a link somewhere
).
From the posts on the Facebook group I've seen the tactic cards that are specific to the KT fanction boxes aren't 'must haves', so not having bought them isn't a 'auto-loss', which had been a concern for me.
Only issue I've found so far is some of the wording isn't the clearest, especially if you don't play 8th ed 40k or, as in my case, it's been a long time since you played
any 40k, but I think a lot of that will be cleared up when the first FAQ is released.
Biggest gripe for me is it sounds like a lot of the tournament players are douchebags, so I won't be bothering to attend events unless I know a lot of the players.