As with modern gaming, pre-orders have become more digital rather than physical items. Different continents will get different items (Sometimes!) Crystal Dynamics released information about the pre orders over 3 stages.
Exclusive 'explorer bundle': Tomb of the Lost Adventurer and the skill upgrade 'Fast Climb'.
Exclusive 'combat strike pack': pistol silencer skill, pistol burst mode skill, headshot reticule upgrade and animal instinct skill.
Digital copy of Tomb Raider: The Beginning comic book.