I haven't read it cover-to-cover yet, either. My brother bought me the book and gave it to me this weekend. I skimmed through with reference to the so-called "non-Biblical" scenes in the film.
Emmerich says that Christ fell seven times. I think He falls five times onscreen. (I'll have to pay more attention next time.
The conversions of Claudia, Abenadar, Longinus "and many other soldiers" -- and, of course, Dismas, the good thief -- are ancient Catholic traditions, and do not originate with Bl. Emmerich. But she does provide some detail of their activites that day.
BTW, she says that Pilate had given Claudia a token when he promised her he would not condemn Christ to death. When Pilte washed his hands, Claudia sent the token to be returned to Pilate, and she left the palace to join the Christians who were in hiding.
She also says that Gethsemane is where Adam wept after his sin. And that after Peter apologized for his denials to the Blessed Virgin, he ran back to Gethsemane and prayed at the same spot where both Adam and Our Lord had wept.