Asimov's masterpiece, rebutting charges that he couldn't write about aliens, sex, or women. The first part and last sections, on Earth and the Moon, are good; the middle portion, with the aliens, is brilliant.
I rather liked the first story ("Cal"), about a robot who wants to be a writer, and the title story has some interesting ideas about a future sensory medium and may give some indication of Asimov's feelings about The Gods Themselves. The rest of the stories are okay, but nothing special.
That's roughly the first third of the book; the rest reprints introductions to other anthologies and editorials from Asimov's Science Fiction magazine (though without any headnotes indicating what came from where; you're left to extrapolate from internal evidence and the copyright dates at the end). On the whole, these aren't worth the bother.