Clearly, Ovid placed this tale next and subsequent to the tale of Byblis and Caunus because he was interested in that juxtaposition. There are a few basic ways in which the two stories are, for all their apparent differences in tone, subject and style, intimately complementary.
The story of Byblis is the tale of a writer possessed by Eros. The tale is the gradual unfolding to consciousness -- first her own, then her brother's -- of her tabooed desire for her twin. The letter, despite elaborate efforts of argument and pathos, fails, and she laments the failure:
She grew pale, hearing that she had been rejected, and her body shook, gripped by an icy chill. But, when consciousness returned, so did the passion, and, she let out these words, her lips scarcely moving: ‘I deserve it! Well, why did I rashly reveal my wound? Why was I in such a hurry to commit things, which were secret, to a hasty letter? I should have tested his mind’s judgment before by ambiguous words. I should have observed how the winds blew; used other lesser sails, in case those breezes were not to be followed; and crossed the sea in safety, not as now, under full canvas, caught by uncertain gusts. So I am carried onto the rocks, swamped, overwhelmed by the whole ocean, and my sails have no means of retreat.’If we were in doubt about her calling to the republic of letters, this revisionary view, and strategic rethinking of her way of revealing her heart, complete with elaborate Odyssean simile, should lay those doubts to rest. The failure to conquer her brother, her reader, only propels her to a more labored manner of grandiloquence. She now begins to conceive a theatrical encounter in which she would act out before his eyes the plot that failed as narrative. Essentially she's covered the poetic territory from lyric to epic to tragic drama in short order. Byblis of Byblos is nothing if not a producer of biblia.