Nickel Creek, the bluegrass trio who’s been in existence for almost 35 years, returns with their first original release in nine years. It’s brainy, it’s theatrical, its twists and turns are not predictable from its authors, who have entered mid-life. To that point, there is lots of middle on this album. The middle’s not the most exciting or thrilling part (see: beginning or ending), but there is plenty happening and plenty to celebrate. The band says that’s the feeling they…