Great timing! Just this week, Library Journal, the main library trade rag, published a column about good reading for adults in the YA section (of the library, in this case). See the column online at The Reader's Shelf: In the Children's Room: YA Reads for Adults.

The plural of "Man in Black" (MiB) is clearly "Men in Black" (MiB), rather than your own "Man in Blacks".