How difficult is it? I would love to take a look and then purchase the appropriate number of copies for my choir of older adults. They’re solid, but also have limits…

Depends on how much familiarity they have with contemporary choral music. There's a lot of mixed meter and a few unusual techniques, but the range is pretty small and all of the dissonances are well-prepared. If they've done any Sven-david Sandström, Dale Trumbore, Caroline Shaw, etc. it's not hard.