There are many complete copies of the Book of the Dead, scattered all over the world now. No two copies are identical. This text wasn't like something churned off a printing press, nor was the religion of pharaonic Egypt dogmatic and canonized, so things like the Book of the Dead were never really standardized. The text came quite close to standardization in the Saite Period (Dynasty 26) but still Books of the Dead from that period show variations.
No single Book of the Dead possesses all of the possible spells, which number more than 180. Most have some version of the most important spells like the weighing of the heart, while some contain spells that most other examples do not. And of course new spells were added along the way. In other words, individual examples of Books of the Dead tended to be at least somewhat specific to the people for whom they were composed.