Downtime, Contacts: https://drive.google.com/open?id=1Z2hUFxu_45hO9Xcd-XyfhWDxwEHYCAqYuKVEOJabFxY
If you're making a character for the first time, you don't need to read all of the rules (there are a lot of rulings -- the original shadowrun rules aren't very clear). Most of the rules deal with stuff that happens well after chargen, or affects things in subtle ways. If you have a specific mechanic you're planning on using for your character (especially for mages), you might want to make sure that mechanic hasn't changed, but otherwise you probably don't need to check the doc.
A few big things that have been nerfed: Quickening, Oversummoning, Adrenaline Boost, Channeling, Superhuman Prowess, Triple Tap, Bound Spirit Armies, Turn to Goo/Petrify, and Multiple Explosions
If you're planning to play a rigger, we've buffed those. You can burn edge to recover drones, repairing is much less expensive, and you definitely use your mentals in place of your physical attributes when jumped-in or piloting in VR.
You'll be able to latent awaken your characters if you decide you don't want to be a mundane forever, and you can use custom drugs once we figure out how they actually should work.