Isaac Asimov & Janet Asimov 
Norby’s Other Secret & Norby and the Lost Princess [EPUB ebook] 

In the second volume of the complete children’s sci-fi series, a boy and his robot venture to a dangerous planet and go in search of a missing princess.Norby’s Other Secret Scheming scientists want to find the secrets behind Norby’s antigravity abilities, but they have to dismantle him to do it! To evade them, Norby and Jeff flee to the planet Jamya, where Norby was created. But can these friends survive a planet is inhabited by angry robots and intelligent, hungry dragons? Norby and the Lost Princess Jeff and Norby travel unintentionally to the distant planet Izz, where they are forced to join a search for the missing princess. Their journey takes them to the muddy world of the Slithers, strange creatures who imprison the travelers, sting them into submission, and communicate with them only through musical sounds. Then things go from bad to worse when they discover that the missing princess has been turned into a tree!