Rudeus narrates his own flaws in a way the anime can't fully show, and the story runs far past it.
Abridged on screen, in full here: Subaru's every thought between deaths, across 40-plus volumes.
On the page you hear the anxious office worker bluffing behind the undead overlord's calm.
Past where the anime stops, all 33 volumes are complete, so Myne's whole climb is there to read.
Rimuru's nation-building gets every detail on the page, and all 23 volumes are out.
The anime covers 5 of 16 volumes, and the spider's frantic inner monologue reads even better.
Two volumes made it to anime. The novel is at 23, and the party's hard climb keeps going.
Shiroe's plans, guild politics and the economics get more room than the anime could give.
The novel runs a finished 17 volumes, well past where the anime has got to so far.
Season 2 was abridged and changed on screen. The novel tells that arc as written, then goes on.