Protector

One of the first Niven novels I ever read - and brilliant it is, too. The concept of a hyper-intelligent entity whose only drive is the survival of breeding members of its own species, was great. The fact that humanity is a long-isolated offshoot of that same species, even more. The fact that we are stuck in an embryonic pre-Protector phase due to lack of a particular plant... priceless.

And of course, the Protector is bringing the plant to us.

This is a brilliant precursor to much of the rest of the Known Space novels and stories, as these keep dipping back into the Phssthpok story, from a variety of angles. A really good read, definitely not to be missed - because it leads on to so much more.