A book series I highly recommend to many is the “Warhammer Horus Heresy” novels.
These books follow the wars and events of the far future, in which the empire of man is expanding and chronicles the conflicts it has with other alien powers.
The books’ main characters are 14 demigod generals known as the primarchs and their armies of super soldiers known as space marines. Half of them fall victim to the dark powers of chaos and swear felty to its dark gods and wage war against rest of empire.
The books dwell on themes of things like Deante’s Inferno and Paradise Lost as they deal with the fall of heroes to darkness and cosmic evil. This evil perverts and mutates humanity, quite literally, into the hordes of hell.
There’s a lot of political and spiritual conflict at the heart of the empire, which is shown to great effect. The books are filled with space magic, demons, space orks and elves – so they often feel like Dungeons & Dragons.
The books have been around since the early 2000s, so there are a lot to read.
But for those who have extra time like me, it’s a great universe to get lost in. So give them a shot.