Either she is writing them herself, or she has hired the most talented ghostwriter in history, one capable of channeling her “voice” flawlessly.
She also has a breathtaking talent for the turn of a phrase. “Death Panels” summed up the fear every intelligent individual has of his most intimate health care decisions being decided by a faceless panel of bureaucrats.
I remember recently that Greta was on talking in perplexity that "she has no entrourage, no staff"--loved that. Just picks up her own briefcase (with her extra shoes) and carries it.
The same, straightforward prose is in her book. I believe she wrote most of it, because it has that distinctive plain, but completely coherent character.