My 7yo boy is interested in astronomy, so I ordered the
"My Favorite Universe" course by Neil deGrasse Tyson from The Great Courses. The suggested readings for the course are below. I think they are written for the general reader, and they have good reviews on Amazon. Other book suggestions are welcome.
Black Holes and Time Warps: Einstein's Outrageous Legacy
by Thorne, Kip
Cosmic Catastrophes: Supernovae, Gamma-Ray Bursts, and Adventures in Hyperspace
by Wheeler, J. Craig
Five Ages of the Universe
by Adams, Fred & Laughlin, Greg
One Universe: At Home in the Cosmos
by Tyson, Neil deGrasse, Liu, Charles
Rain of Iron and Ice
by Lewis, John S.
The Character of Physical Law
by Feynman, Richard P.
The Search for Life in the Universe
by Goldsmith, Donald and Owen, Tobias