All the Pretty Horses isn't quite as grim as other Cormac McCarthy work that I've read but considering that this includes The Road, Blood Meridian, No Country For Old Men and watching the HBO adaptation of his play The Sunset Limited, it's still so bleak that your average person will be depressed enough to be checked into a mental ward and put on suicide watch after finishing it. 
 John Grady Cole is a sixteen year old cowboy in Texas a few years after World War II who was raised on his grandfather's ranch after his parents split up. After his grandfather dies, the ranch is being sold off. With no where else to go, John and his best friend Lacey Rawlins ride off for Mexico. Along the way they hook up with a runaway kid who is nothing but bad news. After getting work on a large ranch, John catches the owner's eye with his skill working with horses, but after being promoted, John falls in love with the owner's daughter which leads to trouble for him and Rawlins. 
 I guess you could say that this is a tragic romance or a coming-of-age story, but that's like comparing The Road to the The Road Warrior. Or saying that Blood Meridian is just a western. Or calling No Country For Old Men a simple crime story. There's a lot more going on than just a couple of kids running off to play cowboy. John and Rawlins get their eyes harshly opened to just how cruel and unforgiving the world can be and that pleasures like young love can't possibly hope to endure in the face of that. 
 As usual, McCarthy's views on life and death and good and evil won't leave any sane person skipping down the street while whistling and looking for rainbows, but he's so skilled that even his grim outlook has a kind of dark beauty to it.