The title of the book—Solaris—is the name of the mysterious planet where dreams creepily come true. Easy, right? But if you've poked around this learning guide a bit, then you probably have a hunch there's something else going on here. Lem's nothing if not an awfully tricky dude, after all.
So here's the trick: The book is about the planet, yes, but the planet is also about the book. You turn the first page and are on the "launching pad" (1.1), you squeeze into the pages where there's "scarcely room to move" (1.2), and soon you're on that other planet, where you can't tell the inside of your head from the outside. The title tells you that this is a book about a book—or a book about how entering a book is like visiting another planet. And in this way, Solaris points to Solaris as much as Solaris points to Solaris.
And you thought science fiction was all bug-eyed aliens and light-sabers, huh?