Unlike a lot of other Jane Austen tributes/continuations etc this one sticks closely to both Austen's characters, values and diction. The problem is that Edmund and Fanny are a pair of her least interesting characters and their romance far less sparky than most. The idea of re-writing Austen from the point of view of her 'heroes' is a nice one, but I didn't really feel that there was much here than we didn't already know from Mansfield Park.
The one really interesting scene is when Mary Crawford and Edmund are rehearsing from Lover's Vows and we get the actual dialogue they have to speak: I don't know whether Grange has invented this or whether she's tracked down a source, but it's both enlightening and slyly funny as Edmund turns almost into a kind of swooning parody of a girl in love.
So overall this is a pleasurable, light read that doesn't violate Austen in the way some 'tributes' do, but still not a patch on the original.