I started reading it once, had a hard time getting through it and stopped before I finished half of it — probably more because of the difficult-to-read style than because of the content.
If you do decide to read it, remember that it is private revelation, and I have been told it was heavily edited by the person who recorded it for the visionary. We are not required to believe private revelation.
So I would rather consider it as one person’s (or two persons’, if you include the person who wrote it down) meditation on what might have happened, rather than “Gospel” truth on what actually happened in the life of Mary.