So the old books will work with the new edition BUT you do need the new chapter afforded munitorium guide, or whatever its called. That's what has the new points costs of units and a few new rules to bring everything up to date for the new edition.
Space Marines and Necrons have been said will be the first new codexes of the new batch. When exactly they'll come out, we don't know. Soonish is the estimate. The rest of them we have no idea. There's been no word on the order or how long the weight. Possibly a new codex every 2 or 3 months.
The starter set seems to come with ONLY the rules for ONLY the units in the box. Not the rest of the space marines or Necrons, and worse, I've been told it doesn't actually explain the rules. It assumes you already have a codex to look up the details. So the book in the starter set says Necron Lords have "My will be done" special rule, but doesn't tell you what that is. You'd have to check the necron book.
Personally, while waiting I'd grab a fee digital copy that can be found floating around the net. No point buying a book that's going to be out of date in a few months, but at the same time you need the book to get started because it doesn't seem like everything is covered in the box set.
