Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Polite & Droll
Ah, Henry James. How droll.
Seriously, though, James' tone in this book is something you'd expect from someone at a swanky dinner party in…oh, let's just say…Paris, 1903. You know, the kind of dude who would say, "So let's get out of these wet clothes and into a dry martini." There's quite a bit of humor in this book, but nothing that's going to make you fall and the floor with a sore stomach.
For example, take this extended metaphor about Strether's relationship to his own enjoyment: "He felt it in a manner his duty to think out his state, to approve the process, and when he came in fact to race the steps and add up the items they sufficiently accounted for the sum" (2.2.3).
LOL, right?
Basically, Strether is so anal, he thinks of himself as an accountant who has to keep track of how much he enjoys everything to make sure he's not overspending on his happiness. Maybe it's kind of more sad than funny, when you think about it. But it's clever in a way that might give you at least a little wry smile. It's totally appropriate for his time, and especially appropriate for a story surrounding a polite, older man like Lewis Lambert Strether.