Why do book groups all read the same books?

We all have choices and vote for the final selection. We have also had some mentioned here:
Behind the Scenes at the Museum
Suite Francaise
Crow Lake
Small Island
Fingersmith
We have read all the ones mentioned in OP, we are looking mainly for ones that you can have a good discussion about.

We have also had
Wind in the Willows
Three Men in a Boat
Tale of Two Cities
Lovely Bones
Cloud Atlas
Life of Pi
Poisonwood Bible
To Kill a Mockingbird
The Secret Life of Bees
Atonement
The Tenderness of Wolves
The Star of the Sea
English Passengers
The Handmaid's Tale
The Story of Lucy Gault
Miss Garnet's Angel
They are just ones that stick in the mind.

We do try and go for ones on special offer or sets from the library-I suppose those 2 facts mean that we tend to cover the same ground as other groups.

oh there's also "Woman on the Edge of Time" by Marge Piercy - a bit of a curate's egg - some fine and convincing writing about abuse of women by the US mental health system in the 60s, but then there's a slightly irritating subplot about a utopian futuristic world.

Okay, crap name and terrible beginning but stick with 'The Magician's Assistant' by Ann Patchett.

A quiet book about the strength of women. Most (if not all) of the dialogue is between women.

I read it a few years ago so it's a bit hazy but I have since searched for all of Ann Patchett's other books.

Not read it properly, have only flicked through it up till now (have put off reading it tbh, will end up doing it at the last minute) It's interesting but rather depressing (brings back some real life memories of my gran's death).

Gah to Jodie Picoult. Although I managed to upset my sister over Christmas by voicing my opinions about JP - must learn to keep my mouth shut sometimes.

our book group is currently reading little women

Am really enjoying it from an adult point of view having not read it since I was 10

God, Jodie Picoult. I enjoy them for a good page-turner but don't want to discuss them! Particularly hate the 'questions for your book group' bits at the back; 'The character X is particularly well written. Why do you think Jodie Picoult is able to write so incredibly well and still blog regularly at her website www.jodiepicoult.topauthors.com?'

oh yes, we did end up doing My Sister's Keeper, for our sins.

We had lots of crap books including The Other Boleyn Girl which sticks in my mind as being truly dreadful, and also the Bookseller of Kabul which was worthy but oh so depressing. Also lots of Jodie Picoult and some pointless crime fiction.

It's a slight element of the lowest common denominator tbh.

for some reason groups are often reluctant to put people off by proposing classics or tough contemporary reads, whereas they are often OK about losing people who want to read more challenging stuff.

We're about to do A Town Like Alice. I'm delighted as I love it, and prob lots to talk about. But my favourite group reads have been War and Peace (would NEVER have read this without group), A Fine Balance by Rohinton Mistry, Blindness by Jose Saramago and of course The Life of Pi by Yann Martel.

I also loved Portnoy's Complaint but thought it very dated and everybody else hated it - very interesting IMO to read 'hot' books of the past, they often seem pretty cold in retrospect.

our book group has read Kevin and Half of a Yellow Sun LOL. But we do usually steer clear of the R & J crowds. This month's choice is The Year of Magical Thinking by Joan Didion, and past choices that went down very well with all of us were Fingersmith, Small Island, The Secret River amongst others.

Richard and Judy
And libraries buy multiple copies of them, so easy to borrow

I think a lot of book groups just follow the Richard and Judy crowds tbh.

Under the Skin - Michel Faber
Any of the Just William books