It's on special at steam, have never played the series at all.
I suck royally at RTS as I hate the whole whoever builds the most of X and rushs wins, my mind won't go there, I am a person who has always gone headfirst and bashed my way through to the other side in the fastest and most brutal fashion I can, but it looks cool, will only be Single Play as I never do multi.
Is this a easy game to get into, should I spring for it?
First and foremost: It's Warhammer 40k, not Warhammer 4000.
This isn't a traditional RTS in single player (the multiplayer is a bit more traditional though). There's no base building and no endless supply of units. You'll usually only control 13 or so space marines per mission, divided into 4 squads with clear and unique abilities. In many ways it's more like a squad-based action RPG than an RTS.