Using a ghost writer is absolutely not wrong, and is often encouraged. Unlike almost any other medium, people have been using ghost writers to put their ideas into readable books with their own names on them ever since Job jotted down God’s inspired words about 4,000 years ago.
Although you can’t steal a Van Gogh and put your own name on his paintings to sell as your own, you must understand that a book is somewhat akin to being part of the soul of the book’s originator: you! It’s your story. It’s your teaching. It’s your idea collection.
The ghost writer’s job is purely mechanical. His or her job requires getting into your mind and conveying your desires for the book to a wide audience. In the publishing world, it’s 100% acceptable and honest to use a ghost writer if you don’t feel capable, don’t have the time, or don’t have the desire to turn your ideas into a complete book.