Download the Nikon D810 insturction manual PDF. The manual covers all the new features and settings available. New items include the i-button, 2 and 3 EV stop choices available in bracketing, electronic first curtain shutter option, split screen zoom display in Live View, the new RAW S for small RAW images.
Of special note are the Bracketing options now include 2 and 3 stops per frame. With up to 9 bracketed frames available, the exposure range is now up to 27 stops!
The ISO range is now 64-12,800. Extended range is ISO 32 and 50 on the low end, and ISO 16,000-51,200 on the high end.
You can also view the D810 Digital Brochure online.