Since water vaporizes without becoming liquid again there is no additional wetting, swelling, or deterioration. Ink will not smudge and the book has better chances of survival.
In fact, vacuum freeze drying results are often satisfactory because no rebinding is necessary, and mud, dirt and soot are vacuumed to the surface, allowing a faster cleanup.
Although some rare or unique materials can be dried successfully by vacuum freeze drying, this process is not recommended for leather and vellum items.
The main disadvantage of vacuum freeze drying is the price because of the equipment required. If required for a limited number of books, the per-book cost can be relatively high.