Interesting book - "Einstein's Greatest Blunder?"
The Cosmological Constant and other fudge factors in the physics of the universe
Donald Goldsmith, Harvard University Press
Just finished it. Didn't realize so much work had been done on identifying dark matter, and how much of that was on "non-baryonic" matter.
Fun read. Light-hearted author, non-technical enough for a nose-picker such as myself to understand.