The Integral Trees is good second-tier Niven, from early in the latter portion of his career, when his writing ability was just starting to fade. Call it his "Silver Age", if you like. In a fractional rating system, I'd give it a 3.6 out of 5.

The story is set in the "Smoke Ring", which is another typical Niven Very Big Object - in this case, one that dwarfs even his Ringworld. Essentially, it's an inhabitable band of oxygen, other gases, water, and life which exists in free fall around a star. It's not stable in the long term, of course, but Niven worked out the physics and apparently it could remain habitable for thousands or even hundreds of thousands of years.

It's a fascinating setting. No gravity! Profoundly alien lifeforms! And, of course, some rather radically changed human beings for characters. The problem is that the characters aren't very memorable or interesting. This is not an uncommon problem for hard science fiction writers - and Niven is generally considered to be the foremost hard SF writer - but in the past, Niven was often able to avoid or mitigate this failing. And short stories, his strongest suit, tend not to need or require particularly strong characterization (in fairness to Niven, he has created some strong and interesting characters in his time - although not always!).

In this case, though, the characters are just flat. Part of the problem, I suspect, is the names. Niven has a weakness for long, consonent-heavy, exotic names - although fortunately he usually reserves them for secondary characters - and you can only read so many four to six-syllable names without having them all run together. Or at least, I can't. Names alone aren't the problem, however. The characters just aren't interesting, with the one exception of an entity that might not be considered a person at all.

Since it's hard to get attached to flat characters, the novel itself never really grabbed me (unlike, say, Niven's Ringworld). It's a well-told story, with lots of adventure, and I'll doubtless read it again. But it's not a great book. Niven has long been one of my favorite writers, and in some of his later books he has showed that he is able to approach if not quite equal the heights of his "golden age" writing. But The Integral Trees is, sadly, second-rate.