I think the morals of The Yellow Admiral by Patrick O'Brian are that blockade duty sucks, politics is everywhere, and don't get attached to new characters on the 18th book of a series as they may not make it out of the chapter alive.
We get a nice look at the characters home life on land again. Jack, as always, has money problems, but Steven does to for a change. They are all living in Jack's childhood estate which he recently inherited. Jack and Steven on land almost seem out of place there, with all the women, children, horses and peasants. Jack endears himself to the peasants by fighting an enclosure, which is unfortunately championed by Jack's commanding officer, Admiral Stranrear, on the blockade. He makes Jack's life pretty awful but Jack pulls through regardless.
There are a lot of fun moments though, especially with Diana. In another scene, when Bonden has a bare-knuckle boxing match with one of Stranrear's gamekeepers. It is quite exciting, though funny, and Steven's care for Bonden after the match is touching.
We don't learn much new in this book but that is not a bad thing. Reading this book really was like visiting and catching up with friends. a 5.