Mr Fellowes - the man who gave us the script of delightful Gosford Park, has written a novel about an endangered species, the aristos who are not yet totally National Trust-dependent. He actually knows people from that rarefied upper-stratum of British society and that insider's knowledge, so to speak, shows. Ms. Nancy Mitford started the genre, I think, and "U and Non-U" is still obligatory reading when you want to laugh at the subtleties that separates greedingly ascending upperclass and land-owning blueblood. It all comes, in the end, to language and accent. (An example of that non-Marxist "class war" literature is Ms Jilly Cooper, of course, but from a below stairs perspective, I'm afraid).
A more serious point is whether the "range" of a writer mirrors his social background or if he can transcend it. Tolstoy has upper nobility characters in his books, and they sound credible, because he was part of that same social set; Dostoevsky never risked going beyond petty nobility, he knew his shortcomings. The spectrum of writing material cannot go too far, in fact. It's frustrating, I know. There goes the fiction that a great writer can bring to live a character from whatever background he chooses.
In Politics something similar happens.You can be a Socialist or a Communist but you'll never be able to "read" well what goes on a Extreme Left mind unless you've been there yourself. The Bourgeois Right cannot understand a practicing Extreme Right skinhead, either. Or, you have to be a former football hooligan in order to write anything meaningful about that phenomenon.
Put it that way, Landowning Aristocrats are extremists.