First Warhammer 40k game.

[hypnotized]

I stumbled into some gameplay on Youtube for this game and fell in love. I had been aware of the series but never really thought anything of it until I did some recent research on the lore (which is ♥♥♥♥♥♥♥ fascinating by the way). Is there any recommended reading I should do before playing through this game to help me get a better grasp storywise? Would this game be considered "canon"? Any other game recommendations I should pick up? Never played the tabletop game and I don't think I will ever get a chance to.

[Vice]

For reading, you could try Space Hulk: The Novel, penned by Gav Thorpe (who was also called in to write the story for Space Hulk: Deathwing). The book focuses on the Blood Angels chapter as opposed to Deathwing's Dark Angels, but it's still all about Dem Hulks.

As for games, you could try the other Space Hulk game on steam, it's a tactical game that's pretty reminiscent of the boardgame actually. As for other 40k games in general, I'd recommend Dawn of War 1 and expansions, they're typical RTS games with 40k flavour and asymmetrical factions. It's almost like a digital version of the tabletop, but with realtime action instead of turn-taking.
Also for third-person action there's the Warhammer 40,000: Space Marine game, which may not be everyone's cup of tea but I enjoyed rather well.

I'm pretty sure this game can be considered canon, as it's an official title with GW's backing, and from the looks of it it's not stepping on the toes of any other official source in terms of things like conflicting events etc.

[Lactose the Intolerant]

The 40k universe is probably one of the best developed fictional non-comic book universes out there, behind perhaps only Star Wars. There's so much reading I wouldn't know where to begin in all honesty. If you look up any books to do with the "Dark Angels" or more specifically "Deathwing" however, you'll be looking in the right place.

The setting of 40k is so vast that there's no reason this game couldn't be considered canon, in this you're just the 1st company raiding a space hulk - that seems to be one of their motive operandi's and nothing lore-breaking happens so far as I can tell.

40k games in general are very hit and miss. Chaos Gate is basically space marine XCOM, if you can get it to work. It has aged surprisingly well and is a lot of fun to play.

Warhammer 40k: Armageddon is on steam and is great if you like turn based strategies.

[Sidonus]

Dude...40k is VAAAAASST lol...but I would say if you are really liking 40k, then try out Spacehulk Ascension...its basically the same game, but its a tactical rpgish rendition of it. Also, if you have not played the original best 40k games out there like Dawn of War 1 and my personal favorite the Dawn of War 2 series....I would personally recommend going to Dawn of War 2 first...damn....daaaamn good series...I have a ♥♥♥♥ ton of hours in DoW 2 lol...still go back and play it after years and years....and it has a pretty good storyline and an ok storyboard/cinematic fluff to it..less of this kinda fluff in DoW 1 though...but that ♥♥♥♥♥ a classic :)

So...basically...what Vice said =P

[XRuinX]

As far as if this is cannon or not, its general consensus that pretty much everything is cannon:

the TT and RPGs encourage players to create their custom lore.

The universe is big enough for most stories to coexist and with warp-magic theres lots that can be done and still plausible for the 40k universe. Matt Ward is like their professional fan-fic writer (he works for GW but his stories break past+current lore, hard).

So yea, the events of all 40k games are cannon, but most of them are original stories, like this one.

Also;
Praise the Urizen!!!!