I've only read two books by Mrs Oliphant (the other being A City Besieged, which is fascinating, weird, and extremely different from this), and enjoyed both. But Miss Marjoribanks makes it very clear why she was a bestselling author in her day. It's a power fantasy, but not unalloyed; it's delightfully snarky, but affectionately so, and well leavened with compassion for everyone on the page. (It's also got the unthinking classism, colonialism, and occasional offhand racism one might expect from a Victorian popular novel, so be warned there.)
Miss Lucilla Marjoribanks comes home from school with the earnest and implacable aim of being a comfort to her dear papa (a widower who, while very fond of his only child, doesn't particularly feel he needs comforting). And, just incidentally, of rearranging the society in her hometown -- for everyone's benefit, of course. What makes this a delight instead of insufferable is the narration's wry wit, and the ongoing martial metaphors. Because, make no mistake, this is the tale of a latter-day Tacitus or Alexander the Great. But one who was born a bourgeois woman in Victorian England, and thus one whose weapons are dinner parties, and whose campaign arena is the drawing rooms of Carlingford. Great fun, a fascinating slice of history, and an excellent diversion from an author who really ought to be better known today.