if to kill a mockingbird in my favourite book...

My favourite book is The Handmaid's Tale.

It's not similar to To Kill A Mockingbird, but you might like it, nonetheless.

A Tree Grows In Brooklyn, Betty Smith.
The grapes of Wrath

The Help is brilliant and along similar lines

It's my favourite too.

And my other favourite is 'The God of Small Things' by Arundhati Roy. It's worth reading if you haven't already.

To Kill a Mockingbird is my all time favourite book too.

I also loved Rohintin Mistry's 'A Fine Balance' and pretty much anything by Sarah Waters and Andrea Levy.

Love Mocking Bird too. Small Island by Andrea Levy is on a similar theme and set a little later-I think you would enjoy that too and when you have read that have you read any Thomas Hardy? I enjoyed Tess of the Durbervilles-prejudice and ignorance come into that .
From time to time I re-read Jane Eyre too. Good luck with the in-laws

The Sweet Hereafter. Not similar plotwise, but some similar themes (small town shaken by an event, the outsiders within the town, etc), and it's beautifully written.

'Cold Sassy Tree' by Olive Ann Burns will appeal if you are a Mockingbird fan.

Catcher in the Rye.
Both that and Mocking Bird have been read numerous times, love them equally.

Roll of thunder hear my cry contains similar issues.

You may like Carson McCullers. The Heart is a Lonely Hunter especially, tho I love them all. Set in the US South. Reminds me of Harper Lee.

You could also try 'Fried green Tomatoes at the Whistle Stop Cafe' And perhaps 'The secret Life of Bees'

YY to A Fine Balance, one of my favourite books.

I enjoyed The Help and The Secret Life of Bees but even better IMO is Sue Monk Kidd's new novel The Invention of Wings. Less fluffy, more hard-hitting and all the more interesting for being based on a true story of the first women from a slave-owning family to become passionate anti-slavery campaigners. An excellent book.

Clover by Dori Sanders

Oh, I loved The Invention of Wings!

The Poisonwood Bible is brilliant. Set in the Congo and has that hot, dry and dusty feel to the setting like TKAM. Also nice and long.

Another vote for A Fine Balance too. Brilliant.

I love TKAM. My favourite book is Eat of Eden. Not similar at all but both great books nonetheless.

The Color Purple?

Love Story - not really similar, but in my mind it belongs along with Catcher in the Rye and TKAM.

The Colour Purple or The Power of One are both quite similar

I like anything by Truman capote. He was a friend of harper lee. And he is Dill in TKAM.

TKAM is my favourite book too... Probably read it over 100 times. It's my go to book if I need my soul to be soothed.