Book was great, I really liked it. I haven't seen the older adaptation yet, but the more recent one (with Clooney) was IMHO terrible. Such adaptations make more harm than good.
The Tarkovsky version is fantastic, definitely find time to watch it. It's visually stunning. Kurosawa wrote about how much he aesthetically loved Solaris, particularly the way Tarkovsky captured water.
Word of warning: do not expect Star Wars or Inception type special effects. And this is Tarksovky's reading which, if you know Tarkovsky, he was concerned more about the human condition, than technological aspects of Sci-Fi.
I both read the book and watched the clooney movie and I liked both of them. The key to enjoying movie adaptations is to imagine they're two completely separate stories that just happen to have certain names in common.
