Classicly

Two on a Tower is a novel by English author Thomas Hardy, classified by him as a romance and fantasy and now regarded as one of his minor works. The book is one of Hardy's Wessex novels, set in a parallel version of late Victorian Dorset. 

The plot concerns two – literally starcrossed – lovers: Swithin St. Cleeve, a very young amateur astronomer, and Viviette Constantine, an unhappily married and abandoned woman 8 or 9 years his senior. Each night Swithin climbs the old tower of the title, in the grounds of the Constantine estate.