On religion she wrote a few religious books. The one I particularly remember is "The Land of Far Beyond" based on Pilgrim's Progress".
I think my favourite series was the Adventure series. My ds wanted a parrot for ages after reading those-we've compromised on budgies.
There's a lot to those books if you reread them as adults that you don't pick up as a child. I remember one where they're fleeing from terrorists and Bill says "Don't worry, Lucy-Ann, they won't hurt children". As a child I took that as read. As an adult you feel the desperate attempt to comfort her, knowing that if they'd caught them probably the best outcome for the children would be killing quickly rather than torturing them to make Bill spill the beans.
Individual stories:
"Five go off in a Caravan" I wanted to do the same. Unfortunately Mum wouldn't consider letting me hire a caravan and go off...
"Rat a tat mystery" Love the snowy scenery.
"Valley of Adventure" beautifully written.
"The Adventurous Four" one of her few obvious WWII stories. Andy was such a good leader.
"The Secret Island" who wouldn't want to live on an island on their own, build a willow house etc...
I find it odd how much she is hated for what a lot of authors of similar era had as well. The huge backlash when Roald Dahl's books were adapted recently-hers were adapted, and often badly, in the 90s.
And the accusations of sexism I do find odd. She had one of the least sexist girls of that era in literature in George. I also, as a girlie-girl found it a bit upsetting. I'd have enjoyed the making up home in the caravan more than the adventure too. So why is it deemed so bad that Anne did? It felt like my likes were seen as inferior.
George is an interesting character, but not necessarily always likable. In that era it would have been unusual for a girl to have a male hair cut and wear boys' clothes, so people will have made assumptions from that rather than particularly how she looked overall.
She's also accused of simplistic language, which I don't think is particularly fair either. She often has the youngest asking, Anne, Bets, Lucy-Anne to explain words and certainly I learnt words reading her books, as well as information I still remember-like how to tell a stalactite from a stalagmite, or a stoat from a weasel.
Her characters are generally 3D, yes, some of her plots are similar, but realistically, how many authors' of 21 book series (Famous Five) don't reuse some aspects? And she wrote over 700 books.
And for sheer emotional writing try "The Rub a Dub Mystery" when Barney thinks he is going to meet his father for the first time and is tricked. The writing is just phenomenal.
My dc all enjoyed her books too, although they read them more as historical fiction than I did.