Most denominational hymnbooks come with an accompanying "companion" or "handbook" volume that gives a lot of extra details about the hymns and authors and tunes and composers, where originally published, and so on. They are wonderful to browse through.
Here's an example:

I know that there are a number of books like 101 Hymn Stories and Come Let Us Adore Him: Stories Behind the Most Cherished Christmas Hymns available in Logos or Vyrso, but those tend to be more devotional in nature and necessarily are selective. Here, for comparison, is the write-up on that same hymn from CLUAH:

And from Amazing Grace—366 Inspiring Hymn Stories for Daily Devotions:

These are nice, but sometimes what you want is more of a handbook/companion style write-up with "just the facts, ma'am!" And these hymnal companions are notoriously unavailable to most church members. The church has the hymnals in the pews, but the companion usually isn't even in the church library (maybe the organist or pianist or worship leader has a copy if they are a real hymn buff, but not likely in a small church), and they are often out of print or expensive. So, I'm suggesting a collection of some of the more important ones.
This would be a real specialist collection, so I'm not anticipating many takers, and thus Logos isn't likely to take me up on this idea. But still, a girl can dream...
OK, that's enough. I realize this would be hard to do, because it's a bunch of different publishers, most of whom Logos doesn't have relationships with yet. But as I said, a girl can dream...