Griffin and Sabine: An Extraordinary Correspondence

Griffin and Sabine: An Extraordinary Correspondence is a trilogy of epistolary novels written by Nick Bantock. The story begins when Griffin Moss, an artist living in London, receives a postcard from a woman he's never met. The woman is Sabine Strohem, a citizen of the Sicmon Islands, who somehow knows things about Griffin's art that no one but Griffin himself could know. Sabine soon reveals that for the last 13 years, she has been able to "see" his drawings and paintings as he is creating them. The two soon become pen pals and begin a long distance relationship, while mysterious forces keep them apart and a strange man investigates their Psychic Link.

Tropes used in Griffin and Sabine: An Extraordinary Correspondence include:

Alternate Universe: Sabine and Griffin appear to be living in two of these.
Epistolary Novel
For Science!: The reason Frolatti wants to study their telepathic connection. In his second postcard to Griffin, he claims the two of them have a "moral and social obligation to allow the scientific community access to your experiences."
Happily Adopted: In her letters, Sabine says she was abandoned as a baby and adopted by an Island couple. She seems to have been pretty happy with them. Griffin was also adopted by Vereker after his parents died.
Love Before First Sight: Griffin and Sabine fall in love through their letters, without ever meeting each other.
Love Transcends Spacetime: Maybe. The two appear to be living in alternate universes. When Griffin tries to visit Sabine in the Islands, he never makes it there and nearly drowns. It's implied that the Sicmon Islands don't even exist in Griffin's universe; in his letter to Sabine after the incident he tells her he wasn't sure if the captain of the boat even knew where he wanted him to take him. The second time they try to meet, they end up staying in the same house for a week without ever coming across each other.
Paparazzi: Victor Frolatti claims that he's a medical journalist, but Griffin and Sabine suspect that he works for a tabloid newspaper.
Parental Neglect: Griffin claims his parents fought all the time and ignored him, so much so that their death in an accident "barely touched him." He saw them more as cartoon characters than actual people.
Sanity Slippage: This may be happening to Griffin throughout the trilogy.
Inner Dialogue: Well, writing to himself, if you go by the theory that Sabine was never real, and was just an imaginary friend Griffin made up.
The Un-Reveal: We never find out for sure whether Sabine and Griffin managed to meet in Alexandria. However, the final letter is adressed to a doctor in Kenya, from Sabine, and repeatedly uses the word "we", so it can be assumed that they are together. Or that Griffin has just gone completely insane.
Uncanny Valley: Griffin apparently found Sabine's self-portrait to be this. Right after seeing it, he writes a postcard trying to break off all contact with her, claiming that he made her up to deal with his loneliness.
Walking the Earth: Griffin spends pretty much all of Sabine's Notebook doing this, while Sabine stays at his house in London.