Ralif Redhammer
Legend
I'd vote for Volo's Guide to Waterdeep. It gives a lived-in feel to Waterdeep, full of rumors that might be true, or might not be. Making Volo semi-unreliable allows for the DM to take the best inspiration from it and discard or alter what they don't like. Two DMs can start with a location in Volo's Guide and have two very different takes. It also gives you that ground-level feel. Knowing how Waterdeep governs is useful, but knowing about the dangerous alleys or wild taverns can be more actionable.
I adore Hallowfaust. It's a fascinating setting that upends the necromancer as villain trope. It's anything but generic and I include it in my games whenever I can.An interesting one for me is Hallowfaust: City of Necromancers from the Scarred Lands. A strongly themed Necromancer magocratic city state, a strongly themed LN necromancer refuge in a hostile monster filled wilderness. It is different in being a place where mindless undead are openly used simply as protection and utilitarian service and non-evil necromancers are openly there and in power. Originally a bunch of necromancers just wanting a safe refuge base to live and do their research it built up with people flocking there for the stability in a dangerous magical post-apocalyptic world.

