The Jewish Bible refers to this book by the fifth word "B'midbar" ("Bemidbar") which means "In the desert", which best describes the contents of this book.
The book of Numbers teaches that; while we may have to pass through wilderness experiences, we don't have to live there! How long we spend "in the wilderness" depends on the strength of our faith and choices we make. For the nation of Israel; the short passage in the wilderness turned into forty long years of agony. This is because of their failure to believe in the promise of God, even after all He had done for them. As a result of their continued unbelief and disobedience, they were to wander in the wilderness for forty years, until that entire unbelieving generation died.