The Mandelbaum Gate by Muriel Spark

To rendezvous with her archeologist fiance in Jordan, Barbara Vaughn must first pass through the Mandelbaum Gate - which divides strife-torn Jerusalem. A half-jewish convert to Catholicism, an Englishwoman of strong and stubborn convictions, Barbara will not be dissuaded from her ill-timed pilgrimage despite a very real threat of bodily harm and the fearful admonishments of staid British diplomat Freddy Hamilton.

Hardcover, 1965

Goodreads: 3.54