Moses Yuriyvich Mikheyev Book order (chronological)

Only friendship has the power to transcend time and space . . . When six-year-old Olivia finds a glowing treasure map that only she can see, she has no idea what it means. But six years later, when a spaceship lands in the wheatfields behind the farmhouse where she lives with her dad, she discovers she has an important destiny to fulfill. She is the Princess of Blue Earth, and only she can read the map that will lead to the Black Ruby, which has the power to heal anything-including her father's cancer. Accompanied by a time traveler boy named Galax, she sets out on a magical and imaginative adventure that will take them to the ethereal beauty of the moon and across the wonders of space in their search for the Black Ruby. But the Black Priests also want the Ruby for nefarious reasons . . . and they'll do anything to stop Olivia and Galax from taking it. For fans of The Little Prince and A Wrinkle In Time.