If I wanted to start my journey into Warhammer 40k lore, what is a good novel or series of novels to start with?
I’d recommend browsing the Lexicanum wiki: https://wh40k.lexicanum.com/wiki/Main_Page
For books, a common recommendation for starting with the setting is the Eisenhorn trilogy (https://wh40k.lexicanum.com/wiki/Eisenhorn_(Novel_Series)). Another common recommendation is reading the first few books of the Gaunts Ghosts series (https://wh40k.lexicanum.com/wiki/Gaunt's_Ghosts_(Novel_Series)).
The lore in this meme (the Razing of Monarchia) is covered in the Horus Heresy novels. If you wanted to jump straight in with the Heresy series it’s generally recommended you read the first five of them^, then branch out into whichever subseries interest you.
^ Horus Rising, False Gods, Galaxy in Flames, Flight of the Eisenstein, Fulgrim
