THE LAMED VOVNIKS (36 Righteous), who appeared in The Book of Names a couple of years ago, make another fictional appearance in a book of stories reviewed in BlogCritics Magazine by Lynda Lippin. Excerpt:

While we do see some back and forth discussions in the Torah, especially in the story of Sodom and Gemorah where Abraham tries to save the cities by bargaining with G-d. While G-d starts out requiring proof of 50 good people to save the cities, Abraham manages to get the number down to 10. Now, we know that there were not even 10 as the cities were destroyed. In the Talmud there is a similar discussion about the number of good righteous people who must exist at any given time in order to keep the entire world existing, and the number is 36.

[...]

The Book of the Unknown is a tale within a tale, opening with a fictional forward by a Professor Jay Katz and closing with a fictional Editor's Note. Professor Katz tells the sory about finding old papers in a German synagogue that was discovered unscathed after the Holocaust, and in the papers discovering a list of 36 names, a list of the 36. Instead of turning the list over to authorities he keeps it and starts to visit the neighboring villages asking about the names on the list, discovering that they all fit the description of the Lamed-Vov. According to the Editor's Note, after publishing some of the stories he mysteriously disappears along with his papers and the list of the 36.

Background here, here, and here.

UPDATE (19 February): Reader Joe5348 e-mails:

The best book using the background of the lamed vov is "Last of the Just" by Andre Schwartz-Bart. It came out, I believe, in 1960 and won about every literary award around. I read the English traslation by, again I believe, Steven Becker.