Any recommendations for a great forbidden romance?

Any (sub)genre is fine, but I would particularly appreciate one set in a spiritual/fantastical/primeval milieu, only because it seems this is where the conflict between spirit/flesh and duty/desire is at its most tortured and grandiose.

Something along the lines of "The Last Temptation of Christ."

Kushiel's Dart is the first book...

very erotic and very well written, lots of romance and fantasy.

http://www.amazon.com/gp/product/0765342987/102-5662130-6768910?v=glance&n=283155&n=507846&s=books&v=glance

one of the best written series I've read, but cannot see letting my son read when he gets older..until MUCH older.

:)

Ayn Rand's books:
The Fountainhead
Atlas Shrugged
or even
We, The Living

Though not top-to-bottom (in a manner of speaking) about romance, they're saturated with "the conflict between spirit/flesh and duty/desire is at its most tortured and grandiose."

Hope you enjoy whatever you choose,
-Drum

Of course, you have to like reading 18th century fiction; Tolstoy was one of the greatest writers ever.

but your post reminded me of a short film by a guy called Nigel Wingrove called Visions of Ecstacy. It's technically banned over here because of the Blasphemy Act. Wingrove appealed up to the European Court of Human Rights, but they ruled:

"Freedom of expression constitutes one of the essential foundations of a democratic society. As paragraph 2 of Article 10 expressly recognises, however, the exercise of that freedom carries with it duties and responsibilities. Amongst them, in the context of religious beliefs, may legitimately be included a duty to avoid as far as possible an expression that is, in regard to objects of veneration, gratuitously offensive to others and profanatory."

Anyway, my moan about British censorship over, the film is based on the writing of St. Teresa of Avila - specifically her descriptions of ecstacy in union with God (what I've seen of the film has her kissing and caressing a naked Jesus). How much is Wingrove's interpretation I have no idea - although a review of the book says "she returns to her own life in order to describe (in erotic language reminiscent of the Song of Songs) the ecstatic experiences given to her by God." You can buy her autobiography as a book:
http://www.amazon.co.uk/exec/obidos/ASIN/014044073

or read it online:
http://www.catholicfirst.com/thefaith/catholicclassics/stteresa/life/teresaofavila.cfm

(but I have no idea of the quality of translation)

This maybe absolutely nothing like what you are after, but hey! I don't do "Forbidden romance"!

You may also be interested in the the following poem, which was published by "Gay News" in 1977 and successfully prosecuted for blasphemy.

The Love That Dares To Speak Its Name
By James Kirkup
http://annoy.com/history/doc.html?DocumentID=100045