The phrase "astonishing stuff" is correct and usable in written English.
It can be used to describe something that is surprising or impressive in a casual or informal context.
Example: "The documentary revealed some astonishing stuff about the ancient civilization that I had never heard before."
Alternatives: "amazing things" or "incredible material".
This is astonishing stuff.
Better Together officials are irate: This is astonishing stuff.
Pretty astonishing stuff, especially in a year when the growth of the Chinese economy actually fell to a three-year low of 7.4 percent in the third quarter.
9.34pm: The Guardian has just posted a tranche of article from the US embassy cables involving Russia, and there's some astonishing stuff here.
I'm working on a second volume of Henry VIII, and I've come up with some astonishing stuff on the crucial changeover from Henry VII that is going to revolutionise our understanding of his reign".
It's an astonishing innings, but as I'd said way back in those heady days of England's early overs, this is doing nothing for my blood pressure". 40th over: Ireland 263-5 (need 65 from 60 balls; K O'Brien 97, Cusack 40) This is astonishing stuff.
"It's the most eccentric restaurant in history... a Sikh guy cooking this astonishing sous-vide stuff on an industrial estate in Nottingham.
One only needs to stop for the occasional gas or rest room break but otherwise you can get an astonishing amount of stuff and people in here.
Graphene is the name given to a novel substance composed of a single layer of carbon atoms, extracted from graphite, with astonishing properties: the stuff is stronger than diamond, more conductive than copper and more flexible than rubber.
It's astonishing all the good stuff Pelecanos can pack into one unpretentious book: meaty substance, multiple story lines, vital characters, choice dialogue and all those descriptive details (about what people are wearing, driving and listening to on their car radios) that make the story so rich.
"It's astonishing how much boxed stuff still comes to the surface," he said, "how often I get a call from the family of a woman who has died, and who left a closet full of dolls put away that she forgot about or never told anyone about".
