Just finished a re-read of the whole 'Bloodlines' spinoff series, and honestly, the lore differences compared to the main 'Vampire Diaries' books are subtle but they're there. The original series by L.J. Smith established the rules – Originals, daylight rings, psychic powers, the whole shebang. 'Bloodlines', written by different authors after Smith, mostly plays in that same sandbox but I think they tweak the emphasis more than overhaul the rules.
For example, the ancient vampire factions and the 'Guardians' introduced in 'Bloodlines' feel like a more formalized, almost secret society version of the lore. It’s less about personal power struggles in a small town and more about these ancient, hidden hierarchies that have been pulling strings forever. The mechanics of vampirism are the same, but the source of their creation and some of the oldest history gets expanded in a way that feels more... bureaucratic, maybe? Not in a bad way, just different. It makes the world feel bigger, but also a bit less wild than the Salvatores' feud did. I kept waiting for a deeper dive into the why of these factions that never quite landed for me.
To me, the real difference isn’t in the lore itself, but in how the characters interact with it. The originals had a frantic, personal energy around discovering the rules. In 'Bloodlines', the lore is often presented as established fact the characters have to navigate, which changes the feel of the story entirely.