Phssthpok the Pak is a Protector: an alien from somewhere in the galactic core. He's travelled for thousands of years on his way to Earth, where he has reason to believe that a previous Pak expedition got into trouble, in the hope of being able to help the survivors.
I think this was the first Niven book I read, must have been around twenty years ago. And I read it more than once, but lent it to someone and have fancied reading it ever since. It doesn't appear to be in print in this country, but I got a copy from abebooks.
What a great story! I only had to read the first page where Phssthpok looks out through his hull made of "twing" to remember how right Wikipedia is to say that Niven is known for his "gee whiz" ideas. Tree-of-life, Belters, duplicate Stonehenge, magnetic monopoles, they're all in here. I'd forgotten, but the way he explains how people who are abducted by the Protector have 4 months of memories erased is a cracker.
The only slight complaint I'd have (which I remember feeling on previous occasions when reading Niven) is that some of his descriptions aren't quite clear enough: for example, when Phssthpok's ship comes alongside Brennan's, it's described but I feel that I can't quite picture it. And the special mini-planet that the Protector builds sounds pretty good but I didn't quite understand how it would look.
But I'm going to have to read some more of the Tales of Known Space now: this book didn't even mention Puppeteers or Kzin, so I'll probably read Ringworld next.
Completed : 13-Feb-2007