I thought about the question for about one year, and I've come to the conclusion that "Stars" is my favorite book of all time. It has tremendous appeal as science fiction, escapism, political and gender theory, satire of modern-day cultural conflicts, and traditional character-driven fiction; and it is a 'novel' in the strict sense. So people looking for any of those things won't be disappointed.
But what I frequently hear from people whom I've persuaded to read this book is that it, somehow, caused them to open their perceptions; to feel that there were more ways of thinking, of feeling, of living than they had previously known. This is Delany's specialty; he did it first in "Dhalgren" but he does it best here, and in this respect no other author can match him. And this is a great talent and a great gift and why Delany will still be read when William Gibson has disappeared down the road that swallowed up Murray Leinster (two of my favorite SF authors, by the bye, and no offense intended.)
Naturally, when something is this good it immediately goes out-of-print. I'd recommend letting Amazon find you a copy - they found me a perfect mint condition first-edition hardcover for $31. I can't recall when I've been so happy about anything.
Oh, and the sequel. Science fiction fans around the world are awaiting it with some annoyance - he did publish the first chapter in 1997 in some academic journal (memory tells me the Journal of Contemporary Fiction, but memory could be way wrong), but it more frustrated and delimited than satiated that desire for closure to the story of Marq Dyeth, Rat Korga, Velm, Nepiy, the Thants, the Xlv, and the mysterious and sinister Web that snares them all. It's anybody's guess if he'll ever finish it, but I certainly hope he does!