Phil .. if you're THAT worried about the reverberant acoustics of the library, and you just said 'people' so there's more than one or two, and it sounds like they're elderly .. I suggest you change the shooting script.

Most older folks can't walk and talk very well so why don't you record their memories off cam to a separate recorder or the cam itself. You'd get a nice clean intimate sound in a damped down office or somewhere, avoiding the reverb. If there's a booboo and there'll be a few .. just redo that sentence.

You might introduce it on cam but have them stroll around the library for some nice dramatic angles. Even go back and shoot more later. In post you can edit it every which way and cover your butt.

So you'll have way more options to work with .. after they've done it to camera that's it, it'll tie you and them down to much.

In that case, I'll bet someone stuffs the narrative up with a bad mispronunciation (librarians hate that) or wrong date or similar .. you'll find out later then have to scrap that take or redo it .. then the light goes etc .. it'll never end.
Hope this helps.

Cheers.

Yeah it would be cool to have them walk through talking among themselves, laved up of course, but with the goal of just getting good B-Roll of their expressions. Then do a sit down interview where they elaborate on the memories that came up on the walk through. Then you play the sit-down audio over the walk through B-Roll. Bam.

Also, if you're worried about the room sounding too live, a LESS SENSITIVE lav can be a better choice than a more sensitive one.

I've always carried both Sony ECM 77b and Sony ECM 44b lavs in my kit.

Lots of times in noisy locations, I'll grab the cheaper 44 because it has a fraction of the "reach" of the 77b.

Now the 77b will intercut a LOT better with my preferred boom mics.

So which lav is "better?" - neither and both.

This is why you can't buy one mic and just stop there. There NEVER will be a single "best" mic for everything - only mics that are proven to work well "under these certain specific conditions."

FWIW