World Book 25: China 3: Masters of Magic is mentioned on page 158 of Rifts Ultimate Edition.
World Book 25 was actually China Two (Heroes of the Celestial Court) published August 2004, while World Book 26 (Dinosaur Swamp) had already been published in June 2004. Adventures in Dinosaur Swamp (WB27) didn't come out until February 2006, after RUE was published in 2005.
Rifter 28 and Rifter 29 both referred to is as "World Book 27" so RUE's "25" being a typo seems likely.