In case i missed it in the OP
i just got into vermintide and am interested in looking up more of this warhammer setting at least
What are some worthwhile novels to read that are set in it if any could recommend some please?
I read far more than I play so can help you out here :-)
A good one to start with is Dark Imperium by Guy Haley, but it's OOP at the moment and almost certainly being rebranded to fit with the newer books as a 'current storyline' book. It covers Roboute Guilliman, a 'primarch' (essentially a demigod son of the Emperor) going into stasis shortly after the end of the Heresy (30k) and then moves forward to a century after his reawakening, after the Indomitus crusade (40k's 'current' setting). He's in a position to have a wide view and opinions on the broken state of the Imperium as a whole.
Spear of the Emperor by Aaron Dempski-Bowden is a good start as it's standalone (although begging for a sequel). A marine chapter with a distinctly Celtic feel is cut off from the Imperium and fighting for survival.
Otherwise, Gaunts Ghosts (Dan Abnett) is like the defining Imperial Guard saga. Start with Ghostmaker, it follows a regiment throughout campaign after campaign as they get worn down, merged with other units, internal strife etc.
Ciaphas Cain (Sandy Mitchell) is also really good. Start with For the Emperor. It's a comedy take on the Imperium based on the Flashman books, in that it follows a Commissar who, by his own admission, is a fraud. The thing is, it's written by an Inquisitor organising his memoirs, and while Cain is harsh on himself, they are actually full of warmth (far more than George McDonald Fraser's original books), he's more human (and competent) than any number of zealots and the sheer pettiness of his observations makes them really good reads. Lots of observations on what the Guard think of general Imperial administrations, xenos, etc. They don't really link into wider lore very much (beyond the odd half-hearted reference to this or that 'big' character in order to needle them) and I love them for that, the sense of satire and knowing takedowns of Imperial bureaucracy, incompetence and nobility underpin what I loved about the setting in the 80s, and feel out it's roots in 2000AD etc really well.
More recently, I've really enjoyed Chris Wraight's books set on Terra, as an introduction to how horrific it is there. Vaults of Terra: The Carrion Throne is great, an Inquisition team picking away at stuff on the throneworld.
For an epic Space Marine saga, Dante followed by Devastation of Baal is a fun introduction to marines as the Blood Angels and their successors face off against a massive tyranid invasion at the start of the Indomitus era. Mark of Faith by Rachel Harrison covers the Adepta Sororitas in the Indomitus Era too, that's a fun story too.
The Horus Heresy series is basically 40k's founding myth that has been kinda retrofitted to underpin the whole setting into a more coherent (well, for 40k) narrative for good or ill, following the shattering of the Emperor's plan for humanity 10,000 years previously. It's a huge series, and I'd probably avoid it until you get your head around the current setting. Pretty much everything is foreshadowing. Although, what is a good read that works almost as a stand-alone, miniaturisation of the Heresy is Know No Fear by Dan Abnett, that shows the Ultramarines led by Guilliman as they see the betrayal firsthand.
One thing that is worth doing is reading a brief introduction to all the factions- either in the main rule book or by looking around online. The novels follow the factions available in the wargame, either as protagonists or antagonists, and some far more than others. Although to be fair most Imperial troops will only have a slightly skewed view of what any of the xenos actually are until they start getting shot at by them :D The vast majority of the books cover one Imperial faction or another, and they make for a good introduction to the setting as a whole as, unlike Warhammer Fantasy, everything revolves around the decaying Imperium far more than it ever did The Empire. Still, there's also some really good viewpoints from elsewhere. Gav Thorpe's Eldar books are much better than his Dark Angel ones. I like Aaron Dembski-Bowden's chaos marine books, and the Necron stories are also interesting as it shows both where they are similar (raw pettiness, jealousy etc!) and how much they differ from humanity.
There are literally hundreds of books, going from relatively shallow battle-after-battle stuff and character studies of how weird everyone and everything is, to procedural thrillers with the investigative characters. 40k is a complete rabbithole of lore. if there's anything specific you're after in a book beyond a good intro to the setting, give me a shout. Otherwise, have a look at which factions appeal to you, and read their better stories :-)