This is book 5 of the "Solar Clipper Trader Tales" series.

This note contains spoilers for the book.

Yeah, Ishmael makes captain. There seems to be a big time-jump again. His captain invites him to sit the captain's exam (which, unlike the others, is by invitation only), and the shipping line owner asks him to take over the Agamemnon, a ship with a very bad reputation.

The ship doesn't make much money, and many of the crewmembers get into trouble groundside all the time. While it's not fought out in detail, it's clear that what are essentially guild protections are keeping them from just getting booted.

This is another one without antagonists. The troublesome crewmembers aren't actively evil; some of them have never been given the faintest clue about their jobs (there's the excuse for the one guy who was supposed to pick cargo that at his previous line he didn't, he just called the line's central bureau, and he kept doing that), and some of them have personal issues they aren't addressing, and some of them just don't have anything better to do. Ishmael puts them all to work, and it works out. (The previous captain seemed like an okay guy, but apparently wasn't doing his job.)

There's a rescue of a ship with environmental problems in there, and some discussion of optimizing astrogation (and going too far in doing so, or not).

He also resolves the problem of having married a stationer, by a quite amicable divorce (arranged without ever confronting her or communicating directly with her).

This one did manage to catch me by surprise at the end; I hadn't expected it to end quite there.