When importing ebooks, a new course is created automatically and all parts of imported book are added into that new course. Course name will be the same as name of the file you are importing.
If you want to import ebook into existing course, just name the file the same as that existing course and it will be added into it.
Lesson name should be the same as course name after importing. In most cases there will be more parts and at the end of name part number will appear ( (1), (2), (3) etc… )