In addition to a fresh set of headshots, each character is given a brief rundown of their personalities and powers, and Reg E. Cathey's Dr. Franklin Storm provides a bit more detail via voiceover. Much of the information leans heavily on the Ultimate incarnations, including Reed Richards' troubled childhood home, Sue Storm's fierce independence and high intelligence, etc. There's a slight contradiction in Dr. Storm's words and the text describing Ben Grimm, with Storm saying he's "uncooperative, disinterested, and far from a team player" and the text describing him as "warm, even sensitive, despite his rough-and-tumble upbringing."
The most fascinating detail, however, is the description of Reed's ability. Instead of having "pliable bacterial stacks" as cells or the ability to shift his body mass as in the comics, this Reed "can warp the space around him, and appear to stretch his body into impossible forms and to incredible lengths."
There's also an "Under the Microscope" section that gives a look at each character's cells. Reed's are said to contain "micro black hole energy," and Ben's seem to be largely made of Zinc.
Explore more at the official website.
UPDATE 4/26/2015 1:00 PM PT: A video containing the voiceovers and "Under the Microscope" graphics has come online. Watch it below: