Two on a Tower
One of Hardy's more experimental novels. A wander into the realms of science, with much metaphysics thrown in.
Lady Constantine falls in love with young Swithin St Cleeve (I kid you not), a lad of (needless to say) lower social class. Yet another re-creation of the "Poor Man and the Lady" motif. And some other typical Hardy tricks; a marriage that isn't, the rustics in the church quire. Of course there are complications, a baby born almost in wedlock, for example. But the main feature of this novel is the way that it centres around a telescope on a tower. Swithin's real passion is for science rather than women.
You can see a parallel with Return of the Native, in that in the earlier novel the main characters played out their lives and passions against the backdrop of the seemingly timeless heath; whereas in Two on a Tower, their loves are set against the entire universe. So how important are a man and a woman? How much damage can they do in their breaches of conventional morality?