Glass bicycle, mental power, additional organ, organ removed at death, "I return to the sub-abbasa"

[TMR]

Hi those or the main points I recall of a Sci fi novel I read ages ago.
A human explore lands on a planet in search of ... new race / advanced tec, only to be disappointed by aliens riding glass bicycles. Eventually he discovers "they" have an additional organ which grants them extraordinary mental powers. "He" was searching for help as earth had revived an Alien that has extraordinary mental powers, and has basically taken over the world. "He" ends up transplanting the organ into his own body, and commences to fight the Alien.