His books decrease in quality the later you go.

One of his older ones (Hyperspace) is quite good and filled with lots of real science and math. Visions is pretty good too.

I think he leaned into the TV spots and airplay a lot and ultimately, fantastical stuff sells better. And now it doesn’t matter what he says, it just makes money.

See Neil DeGrasse Tyson for a similar story, though perhaps at a different point in his career.