Friends of the Great Barrington Libraries will host a free screening of the documentary "Ay Mariposa" at 7:30 p.m. Saturday, Dec. 7, in the reading room of the Mason Library. Doors will open at 7 p.m. for a wine and cheese social.

The film and social are free and open to the public.

The December book sale is open during regular library hours through Jan. 1 in the main reading room. Each book costs $1.

Information: 413-428-2403.