The Starfinder book is massive. Fortunately Paizo has got you covered.
Starfinder was a smash hit at Gen Con, and now it’s officially launched everywhere. Doubtless you’ll get your hands on it soon enough, then you too can dive into the 528-page rulebook and start figuring out all the minutiae.
You can head down to the bottom of this article and find a direct link to the cheat sheet/quickstart rules and hAve all the tools you’ll need to stay playing today!
Starfinder has a ton of differences from Pathfinder, both glaring and subtle, one of the things we shot for in the design was making sure that if you know how to play Pathfinder, it’s a fairly easy switch over to Starfinder. Toward that end, Starfinder Design Lead Owen K.C. Stephens has crafted this handy one-page “cheat sheet” to help you jump straight into the action. While these notes on key rules and differences between the two games is by no means exhaustive, and no substitute for actually reading the Core Rulebook, it should provide some helpful reminders and make it easier for your gaming group to dive in and start adventuring right away.