One of the best is 'Horus Heresy'. It details the great betrayal within the Imperium. It's full of epic battles, complex characters like Horus and the Emperor. Another great one is 'Gaunt's Ghosts' which follows the Tanith First and Only regiment through various campaigns, showing their camaraderie and struggles in the grim darkness of the 40k universe. And 'Eisenhorn' is also highly regarded as it follows an Inquisitor on his dangerous quests to root out heresy.
There's also a fanfiction called 'Emperor's Will'. In this story, it delves deep into the Emperor's thoughts and plans that were perhaps left unfulfilled during the original lore. It shows how his will could have been executed differently to change the fate of the Imperium. This fanfiction is quite detailed and really makes you think about the Emperor's capabilities and intentions.
One great Warhammer 40k fanfiction is 'The Emperor's Gift'. It delves into the relationship between a Space Marine and a young psyker. The story is full of action and the exploration of the complex lore of the 40k universe. Another is 'The Lost Legion', which offers a unique take on a lost chapter of Space Marines and their journey to regain their honor. And 'Sister of Battle: Redemption' is also excellent, following a Sister of Battle on her path of atonement and her battles against the forces of chaos.
Some of the best Warhammer 40k novels include 'Horus Rising' by Dan Abnett. It gives great insights into the early days of the Horus Heresy. Another good one is 'Gaunt's Ghosts' series which follows the Tanith First and Only regiment and their many battles.
Definitely 'Horus Rising'. It's like the gateway to the whole Warhammer 40k saga. It sets the stage for so much of what's to come. You learn about the politics, the power struggles, and the different factions within the Imperium. It also has some really cool battle scenes that show you what the combat in this universe is like.
I'd recommend 'Horus Rising' as a great one to start with. It's the first book in the Horus Heresy series which is a huge and important part of the Warhammer 40k lore. It gives you a good introduction to the Space Marines, the Imperium, and the main characters like Horus. You get to see the events that start the whole downward spiral for the Imperium.
I think 'Eisenhorn' by Dan Abnett is a great choice too. It focuses on Gregor Eisenhorn, an Inquisitor. The novel does a wonderful job of exploring the political intrigue, the horror, and the moral ambiguity within the Warhammer 40k setting. It has a really engaging mystery element that keeps you hooked from start to finish.
Another great novel is 'Eisenhorn' by Dan Abnett as well. It focuses on the Inquisitor Gregor Eisenhorn and his investigations. It's a really engaging read as it delves deep into the mysteries and the darker side of the 40k universe, with lots of action and interesting characters.
I think 'The Emperor's Gift' is a great starting point. It has a self - contained story that is easy to follow. It involves the Space Wolves and their encounter with a strange alien threat. The novel does a good job of showing the unique culture and combat style of the Space Wolves chapter within the Warhammer 40k universe.
Some of the best include 'Horus Rising' by Dan Abnett. It sets up the Horus Heresy really well and gives great insights into the characters. Another is 'Gaunt's Ghosts' series which follows Colonel - Commissar Ibram Gaunt and his regiment through many battles. And 'Eisenhorn' by Abnett too, it's a great look into the Inquisition in the Warhammer 40k universe.