Loved Piranesi and Station Eleven, bounced off Cloud Atlas at page 80 — what is the thread and what next?

I read the thread differently. It is not voice, it is melancholy plus institutional strangeness, a person quietly doing their job inside a system that does not explain itself. Piranesi is an archivist, Station Eleven is a troupe with a route and a schedule. On that reading, Klara and the Sun and Annihilation are both closer to your centre than the fragmentary ones, and Annihilation in particular is a single narrator on a single expedition with no structure to hold. I would also gently say Cloud Atlas is a bad diagnostic, half the people who love your two books bounce off it.

The thread is one close voice inside a world whose rules are withheld and then revealed slowly, and Cloud Atlas breaks exactly that by handing you six voices and asking you to hold the structure in your head. Both of your favourites also have a narrator who is fundamentally kind, which sounds soft but is doing a lot of the work. On that basis I would give you The Employees by Olga Ravn, which is short, strange and told in fragments from a single institutional setting, and The Wall by Marlen Haushofer, which is one voice, one situation, no explanation. If you want the sadder end of it, Never Let Me Go does the withheld rules thing about as well as anything.

Read The Wall. Then decide whether you want more of the quiet or more of the strange, because they fork after that.

Practical note on the commute constraint, since it is doing more work than people think. I tracked my own reading for a year and found that anything with chapters over about 15 pages had roughly double my abandonment rate, purely because I could never finish a chapter in one leg of the journey. Both of your favourites have short sections. Filter for that before you filter for genre and your finish rate will jump.

The mistake I made in your position was taking a thread like this one, buying twelve books at once, and reading two of them. A stack of unread recommendations turns into an obligation and then into avoidance. Take one, read it, come back and say what did and did not land, and you will get a far better second recommendation than any list gives you.