The Custom of the Country: Undine is a bore, and other things

I finished reading The Custom of the Country a few days ago. 
I think the power of The Custom of the Country starts to diminish after Ralph Marvell’s death. Undine Spragg is a magnificent creation, a complex, vivid character, but some of the most poignant and moving writings in the novel are about Ralph. 
I wish there were more of Raymond de Chelles, or, to be specific, I wish we had access to his mind the way we could enter Ralph’s. 
Undine’s marriage to Raymond is not really a repetition of her marriage to Ralph, as some readers complain. Indeed there are a few similarities, Ralph and Raymond are both not “new money” (Ralph is from an old New York family and Raymond is a French aristocrat), both are not rich as Undine has hoped and cannot keep up with her extravagance, both are cultured and intellectually superior to Undine, both fall for her beauty then realise that she’s a bore and a philistine, both follow social rules and traditions and disapproves of Undine’s disregard for them and association with “the wrong set”, and so on. 
1 of the main differences is that de Chelles are French aristocrats and have stronger customs, to which Undine can’t adapt, and her marriage is one of ennui, as she’s stuck in the country all the time, bored, unable to go everywhere and have fun as when she’s married to Ralph. 
It is during this time that Undine starts to realise she’s a bore. 

“Raymond was as "lovely" to her as ever; but more than once, during their months in the country, she had had a startled sense of not giving him all he expected of her. She had admired him, before their marriage, as a model of social distinction […] But Raymond, to her surprise, had again developed a disturbing resemblance to his predecessor. During the long winter afternoons, after he had gone over his accounts with the bailiff, or written his business letters, he took to dabbling with a paint-box, or picking out new scores at the piano; after dinner, when they went to the library, he seemed to expect to read aloud to her from the reviews and papers he was always receiving; and when he had discovered her inability to fix her attention he fell into the way of absorbing himself in one of the old brown books with which the room was lined. At first he tried—as Ralph had done—to tell her about what he was reading or what was happening in the world; but her sense of inadequacy made her slip away to other subjects, and little by little their talk died down to monosyllables.” (Ch.39)  

Like Ralph, Raymond tries to engage Undine in his interests and conversations but gives up after a while, but only the quiet of the French country, without distractions, forces her to realise that she bores him, something she never noticed before.   
Hear this from her friend Madame de Trezac (formerly Miss Wincher): 

“"Well, you don't work hard enough—you don't keep up. It's not that they don't admire you—your looks, I mean; they think you beautiful; they're delighted to bring you out at their big dinners, with the Sevres and the plate. But a woman has got to be something more than good-looking to have a chance to be intimate with them: she's got to know what's being said about things. I watched you the other night at the Duchess's, and half the time you hadn't an idea what they were talking about. I haven't always, either; but then I have to put up with the big dinners."” (Ch.42) 

Undine can get away with her ignorance in New York society, but not in French society. 

“When Raymond ceased to be interested in her conversation she had concluded it was the way of husbands; but since then it had been slowly dawning on her that she produced the same effect on others. Her entrances were always triumphs; but they had no sequel. As soon as people began to talk they ceased to see her. Any sense of insufficiency exasperated her, and she had vague thoughts of cultivating herself, and went so far as to spend a morning in the Louvre and go to one or two lectures by a fashionable philosopher. But though she returned from these expeditions charged with opinions, their expression did not excite the interest she had hoped. Her views, if abundant, were confused, and the more she said the more nebulous they seemed to grow. She was disconcerted, moreover, by finding that everybody appeared to know about the things she thought she had discovered, and her comments clearly produced more bewilderment than interest.
Remembering the attention she had attracted on her first appearance in Raymond's world she concluded that she had "gone off" or grown dowdy, and instead of wasting more time in museums and lecture-halls she prolonged her hours at the dress-maker's and gave up the rest of the day to the scientific cultivation of her beauty.” (ibid.)   

Another difference between Ralph and Raymond, which is more important, is that Ralph’s very soft and easy, whereas Raymond is very firm, not letting Undine have everything she wants. 
For example: 

“She had accepted all these necessities with the stoicism which the last months had developed in her; for more and more, as the days passed, she felt herself in the grasp of circumstances stronger than any effort she could oppose to them. The very absence of external pressure, of any tactless assertion of authority on her husband's part, intensified the sense of her helplessness. He simply left it to her to infer that, important as she might be to him in certain ways, there were others in which she did not weigh a feather.” (Ch.39) 

Later: 

“The incident left Undine with the baffled feeling of not being able to count on any of her old weapons of aggression. In all her struggles for authority her sense of the rightfulness of her cause had been measured by her power of making people do as she pleased. Raymond's firmness shook her faith in her own claims, and a blind desire to wound and destroy replaced her usual business-like intentness on gaining her end. But her ironies were as ineffectual as her arguments, and his imperviousness was the more exasperating because she divined that some of the things she said would have hurt him if any one else had said them: it was the fact of their coming from her that made them innocuous. Even when, at the close of their talk, she had burst out: "If you grudge me everything I care about we'd better separate," he had merely answered with a shrug: "It's one of the things we don't do—" and the answer had been like the slamming of an iron door in her face.” (Ch.41) 

This is particularly interesting because for once, her weapons fail, as she meets a force stronger than her own. Unlike other people including her parents, he can resist her.  
When writing about Undine’s marriage to Raymond, Edith Wharton chooses to focus on Undine’s perspective—her ennui, disillusionment, and growing realisation of her own deficiencies. It may just be my opinion, but I can’t help thinking that Wharton makes a mistake in making readers curious about Raymond but not giving access to his thoughts. Her approach certainly makes Undine more real—Undine becomes more human, as her charms and threats don’t always work, and more complex because she knows it, and knows that in some circles she can be a bore. 
I just wish we knew Raymond’s thoughts, especially when Paul (Ralph’s son) loves Raymond the most (and forgets his own dad). Undine, even when capable of recognising her own ignorance, is hollow and quite unbearable.  
Overall, The Custom of the Country is a brilliant novel, an interesting study of a female social climber who gets everything she wants but for whom nothing is enough. The House of Mirth is a greater novel because of Lily’s dignity and moral choice, but The Custom of the Country should be read for the power of characterisation and Edith Wharton’s writing, and of course, the character of Ralph Marvell.