I just want to say that I don't really think MGs are getting edgier, I think that people just don't realise how dark they have always been. Yes an MG might not deal with finances, though they can certainly deal with poverty etc (heck the Ramona books had a lot to do with how little money her family had), but murder/death and crime? That stuff has been in MG since forever. Just read Peter Pan
. Or Goosebumps. I'm not saying one must go dark suddenly to write MG, but that there really is a great deal of subject matter that can be covered, and really, as we've have been saying it's really a lot more about voice and how the subject matter is handled than the subject itself.
I agree. I'm surprised that people haven't actually read a lot of kids books with dark themes already though. Didn't they read them as children? I think books for this age group are getting less "edgy" because a lot of modern attitudes towards parenting and children is veering towards over-protection and "helicopter" parenting. (Not everyone of course. But the prevalent attitude.)
The Secret Garden (F Hodgson Burnett): Mary's parents die in a cholera epidemic, all the household servants flee, terrified they'll get cholera. Mary's left in the house all alone, completely forgotten, until she's discovered by soldiers. Later in the book, there are hints that a boy who's an invalid, Colin, is not actually ill/disabled and never had been; his doctor's been trying to make him die so he can inherit the Mistlethwaite estate, so has kept him in a back brace and not allowed him to learn to walk or even play. (A lot of people read it as Colin being born with a disability, but having read the book about 100 times, he wasn't, he was born prematurely and his doctor put him in a back brace, severely restricted what he was allowed to do and made him afraid to go outdoors and no medical justification was given for this and the doctor would've inherited the estate if Mr Craven died without an heir.)
James and the Giant Peach (Roald Dahl): James's parents are killed by an escaped hippo then James (who is only 5 at the time) is sent to live with abusive aunts who make him sleep on the floor or even outside and spend his days chopping wood and doing other physical labour and not allowed to go to school or even meet other children. They verbally abuse him regularly and treat him like a slave.
What Katy Did (Susan Coolidge): MC breaks her back falling off a swing because she didn't listen when her aunt told her that the swing wasn't safe and needed to be fixed. She's bedridden for months and no-one knows if she will ever walk again.
The Little Princess (F Hodgson Burnett): the MC is a rich girl with a loving father who spoils her (but not enough to make her mean and unpleasant) and she goes to an expensive, exclusive school where she's treated like a princess. Then her dad dies and loses his fortune just before he dies, so all of a sudden she has all her belongings taken from her and she's forced to work in the school as the lowest of the low among household servants.
There's also I Am David by Anne Holm (although that might be classified as YA with a younger protagonist - according to Wikipedia he's 12 but when I read it I mentally pictured him as being a bit younger, but the tone and way it's written is more YA, and the depiction of the events and emotions is more subtle) about a boy who's lived in a Nazi concentration camp for as long as he can remember, who escapes and makes his way, alone, across Europe (facing all kinds of dangers and difficulties) trying to find a home and family he's doesn't remember. All he knows about his identity is that his first name's David.
Contemporary examples (because, you know, raiding your kids' bookshelves and that...):
Wonder (R. J. Palacio): my 11 yr old totally raves about this book but I've not read it myself yet. It's about a boy with a facial deformity and how he's (mis)treated by people around him. My daughter says it's guaranteed to make anyone cry.
The Boy in the Dress (David Walliams): the MC's mum died (before the book starts) and his dad and older brother's way of (not) coping is to ban anyone from talking about her. The MC is punished and humiliated by his dad for having a secret photo of his mum. He's into fashion and dresses but his dad tries to force him to conform to gender stereotypes.
The Illustrated Mum (Jacqueline Wilson): the MC's mum has bipolar disorder, which is not being treated and she doesn't realise she's becoming ill and therefore doesn't see a doctor. As her mum's mental health spirals out of control, the MC and her sister are left to try to look after themselves and keep the household running and pretend to the neighbours, school, etc that everything's normal, while they are being severely neglected and trying to understand their mother's increasingly erratic behaviour. Their mum ends up in a psychiatric hospital before she finally is able to get medical treatment.
IMO the main thing with this age group is that there is hope and a change of fortune for the characters that are in bad situations. I can't think of any books aimed at this age group that have a tragic ending. Even Roald Dahl's The Witches isn't a properly tragic ending, though many people may consider a child being permanently turned into a mouse and having the livespan that goes with it to be just that, because the MC himself sees it as a good thing because his lifespan and his grandmother's is going to be the same length so they can enjoy all their days together. David Walliam's Gangsta Granny has a sad ending (not going to say what it is but you can probably guess) but still ends on a positive, hopeful tone so isn't a tragic ending. I don't think writers should shy away from having really bad situations or terrible things happen, but the overall tone needs to be hopeful and bad things balanced out by good things, humour, overcoming adversity and a hopeful attitude. Most of the examples above, after the bad things happen, things get better and good or even magical things happen (like a strange old man gives you magic beans, which, horror upon horrors you lose because you trip over the roots of the old dead peach tree in the garden and all the magic beans escape, but then the tree suddenly grows a peach... which grows and grows and grows and grows...).
Also, the way tragic events are depicted is a lot more straight forward and doesn't dwell too much on the misery. It's viewed through a child's eyes, i.e. very matter of fact, the way children just accept the reality around them because they're not old enough to know any different. (Which can make it all the more poignant, especially if you read the book as an adult.)