Kelvor Ravenstar
Explorer
The new paperbacks don't invalidate any old classes, they're just introductory books with new classes. So you're invoker is still around, and in the new online character builder.
But if you're playing in a game I'd recommend the Rules Compendium. It has all the rules needed to play (except Rituals) in one convenient smaller size. And there are a few tiny rules updates included in it, as the skill DCs have changed again (Making the easy DCs easier, and the hard DCs slightly harder), the only other change I've found that I can easily remember that characters charging with reach weapons can now end their charge adjacent, rather than one square away.
But if you're playing in a game I'd recommend the Rules Compendium. It has all the rules needed to play (except Rituals) in one convenient smaller size. And there are a few tiny rules updates included in it, as the skill DCs have changed again (Making the easy DCs easier, and the hard DCs slightly harder), the only other change I've found that I can easily remember that characters charging with reach weapons can now end their charge adjacent, rather than one square away.