An interesting work of science fiction. The book has a quiet dreamlike quality and explores ideas in an interesting fashion. It has a truly unknowable and incomprehensible alien at its core: a world spanning ocean. Solaris is pretty clearly one of the most interesting aliens ever written and so alien that it is not even clearly a living creature.
The science in the book is at times willfully silly and that gets in the way of what is otherwise quite a good book. It explores the inner workings of the soul and to some degree it is about the fact that we cannot understand the workings of the universe. It explores dreams and memory. There is something about it that was reminiscent of Lovecraft for me.
The characters are flat and the writing is a bit drab and this stops the book from being rated higher. In some ways it is about a mood and is only partially successful in invoking that mood.