The following genres, authors, and specific books have been suggested for forming reading groups around:

Genres & Time Periods (Feel free to suggest more!):

Debut Novels
Young Adult Lit. (YA)
Children's Lit.
Fantasy
Chick Lit.
Mysteries
Historical fiction
20th Century Lit.
19th Century Lit.
Southern Lit.
History
Biographies
Memoir
American literary fiction
British literary fiction
Canadian literary fiction
Literature in translation (especially Spanish, Portuguese, Latin American)
Upscale Horror
Romance
Science Fiction
Magical Realism

Authors:

Charles Bukowski
Edith Wharton
E.M. Forster
Gunter Grass
Haruki Murakami
Henry James
Isabel Colegate
Jan Mark
Jane Austen
Jane Gardam
Kafka
Louise Erdrich
Ondaatje
Penelope Lively
Sarah Dessen
Tolstoy
Umberto Eco
Victor Hugo
Virginia Woolf
William Faulkner
Wallace Stegner
Yukio Mishima

Specific Books:

Afterwards by Rachel Seiffert
Annie Freeman's Fabulous Traveling Funeral by Kris Radish
As I Lay Dying by William Faulkner
Coraline by Neil Gaiman
Didius Falco by Lindsey Davis (Historical fiction)
Eat, Pray, Love by Elizabeth Gilbert
Icebergs by Rebecca Johns (PEN/Hemingway finalist novel)
The Riders by Tim Winton
Running with Scissors by Augusten Burroughs
The Sharpe Series by Bernard Cornwell (Historical fiction)
Stephenie Meyer series
The Sound and the Fury by William Faulkner
The Shadow of the Wind by Carlos Ruiz Zafon
In Cold Blood by Truman Capote
Faith Club by Ranya Idliby et al.
Devil in the White City by Eric Larson
The Ha Ha by Dave King
I the Divine by Rabih Alameddine
Lying Awake by Mark Salzman
Painted Drum by Louise Erdich
The Antelope Wife by Louise Erdrich
Four Souls by Louise Erdrich
Love Medicine by Louise Erdrich
The Time Traveler's Wife
Testimony by Anita Shreve
Sarah's Key by Tatiana de Rosnay
The Birthing House
The Unbearable Lightness of Being