They tempt one another to guess what they look like. And did you really Google me? How flattering!' They start off teasing – 'I like your humour,' writes Emmi, 'it's only a semitone away from chronic seriousness.' And then things start to develop.

It's the beginning of a modern romance: 'Dear Mrs Rothner, I'm so glad you've written back. In Love Virtually, Leo Leike and Emmi Rothner start corresponding by accident one slight slip in an email address, and suddenly they're away. But they remain unusual enough, or odd enough, as devices, or forms, to get the reader's attention – like gentians instead of roses on Valentine's Day. Hardly bobby-dazzling: there are, obviously, numerous epistolary novels, and email novels, and postcard novels, and blog novels, and novels written as dictionaries, and abcedariums. Glattaeur writes his novel of love as an exchange of emails Levithan writes his as a dictionary. So, how to write about a subject that everyone else has already written about, and everyone has already read about? It's a simple, practical question with a simple, practical answer. You name it, we've read about it: falling in love falling out of love making love forbidden love love found love lost love aches love pains lovers' tiffs. It's been around the block a few times, of course – A Lover's Discourse Antony and Cleopatra The Art of Loving As You Like It Pride and Prejudice The Allegory of Love Love in the Western World Love in the Time of Cholera Bridget Jones's Diary Dr Zhivago.

But there's more to it than that – isn't there? 'Love's limits are ample and great,' writes the very ample and great Robert Burton, in An Anatomy of Melancholy, 'and a spacious walk it hath.' In Love Virtually and The Lover's Dictionary Daniel Glattauer and David Levithan give it another good outing. At least according to biological theory, as described in Sheila Sullivan's indispensable guide Falling in Love: A History of Torment and Enchantment. the eyes dilate, the heart beats faster, the rate of breathing rises, and it is possible that the excited body also puts out aphrodisiac chemical odours.' Congratulations! You're in love. 'T he sex organs engorge, the skin tingles.

Daniel glattauer books