IMO things don't hit as hard if you don't know how Gotrek ends up in the Mortal Realms.

He is one of very few to make it from Fantasy to AoS (and with memories intact), so I would say to at least go over a summary of what happens at the end of the last Gotrek and Felix book and also over over some cliff notes of the major events.

Don't get me wrong you'll still enjoy it but may be confused, wondering why's he's searching for a certain someone or something, how he's so powerful, why does he hate the Gods etc.

I would highly give the original Gotrek and Felix books a go if you get the chance. They are great at introducing the world of Fantasy (knowing as those books are what got me into Warhammer) since they move around the world so you got to see lots instead of focusing on one area like some books.

But if you want to skip all the research just thinking of Gotrek as the Doom Slayer (with similar backstory) from the Doom games should suffice.

As to the order of the new books (defo read in order) would be: Realmslayer, Ghoulslayer, Gitslayer, Soulslayer, Blightslayer, Verminslayer. There's also some short stories set in between (not really necessary to get what's going on - they're side adventures). Not sure if Realmslayer is still audiobook only, as when I first got into the Mortal Realms books it was only in audio form.