This book includes a few brilliant stories. First (in terms of quality, chronological order, and position in the book) is To See the Invisible Man, a fascinating and well-written take on the concept of shunning. There's Going Down Smooth, about a broken AI psychiatrist; the theme is nothing new today, but I am guessing back in 1968, before cyberpunk was invented, it may have been revolutionary. Then there's The Pleasure of Their Company, a very interesting story about guilt, loyalty, and delusion; and After the Myths Went Home, a compact, tightly-written story with a very satisfying ending.
So: four short stories that I truly recommend everyone to read.
Unfortunately, the rest of the book consists of generally unsatisfying and sometimes mediocre writing that I doubt would appeal to anyone who does not share Mr. Silverberg's sexual hangups. (On the other hand, if the concept of a human male temporarily marrying seventeen alien sisters is as titillating for you as it clearly is for the author, then hey, this book just might be perfect for you.)
Anyway, the question you should ask yourself is, are 4 excellent short stories (+ ballast) worth the $23?