Daelyn Lizzy’s review published on Letterboxd:
Go, read the book.
I find the movie confusing... It's just that the exposition and events are presented in a way that it is really hard to figure out what is going on. I know very well that the theme and nature of Solaris is all about confusion, but it should be a confusion about "what is Solaris, and what are guests?" and not a general confusion about what are the events presented.
I think that casting was misplaced. Not before the actors were bad, but because I could not suspend my disbelief and only saw Clooney, girl from Truman's Show, and guy from Lost, instead of the characters the movie is supposed to be about.
Solaris itself has lost all of the identity from the book. It's whole nature and behavior was to be confusing. The structure it creates, the way it responds (or doesn't) to probing. The movie lost a lot by reducing it to glowing ball, and making the guests it's only active creation.