What The Ambassadors is "about" (as James would put it)

Finished "book 2" (of 12 - isn't the term "book" kind of pretentious for a 30-page section) in Henry James's "The Ambassadors" and taking stock of the central question: what is The Ambassadors about? (Or, as James would put it, what is The Ambassadors "about"?): definitely the central James theme of the new world - old world conflict, as it centers on two middle-aged American men, Strether and Waymarsh, traveling (together) through Europe: Waymarsh has been there for some time and is thoroughly sick of Europe and wants to return - he's ended a bad marriage and is, apparently, kind of hyperkinetic and fairly well off; Strether, the main character of the novel, is 55, widowed, and lost his only child to diphtheria some years ago - he feels guilty about more or less ignoring his son after his wife died. Oddly, we don't learn much of his back story until well into the novel, and even then it's rather glancing - but what we do learn is that Strether is emotionally dead: he has few connections with people, few or no interests; he is also for some reason ashamed by his American background, which is less socially prestigioius than that of Waymarsh - he's from some small Connecticut town (fictional name), where a woman , presumably of about his age, named Mowsley (or something like that, has sent him on a mission: to "rescue" her son, Chad. Chad is living in Paris, with some sort of Bohemian, as they'd say then, young woman and dabbling in the arts - in other words, he seems "lost" to his straightlaced New England mother. Strether has no idea how he will rescue Chad or for that matter whether Chad needs to be rescued - but we can see the outlines of what is most likely to happen: encountering Chad in Paris is likely to convert Strether rather than to revert Chad. We'll see. Several underlying and unexamined themes: the homo-erotic attraction between Strether and Waymarsh; the odd relation between Strether and the woman who latches on to him in England and considers herself to be some sort of "guide" - but to today's readers would seem much more like an escort - who is she and what does she really want?; and the back story between Strether and Mrs. M. from Connecticut - why has he undertaken this task for her (she's quite the nudge, writing to him almost daily) and what will he get in return? Money? Status? He does not by any stretch seem to be in love with her.