Book confirms length of the class as 630 meters.
(By comparison, the Avenger class in STO is 430m).
It reveals no new in-universe details about the ship and class.
Background material includes STO (Perpetual Entertainment era) concept art, and it's discussed how the ship was based on a concept for a game. STO is not referenced by name, for some reason.
New tidbit: The ship was originally meant to be a Starfleet cargo ship appearing in a background shot in eps four or five, and specifically have a 120m-wide cargo door at the front. This is where the little landing bay at the upper bow of the Zheng He comes from.
After the cargo ship was dropped in revisions, there was not meant to be ANY Starfleet ship in the season. Until Eaves got a call to present a Starfleet ship for the season finale. He finished the drawing in one hour, emailed it, and it was VFXed within weeks.