If you read Margaret Starbird's book THE WOMAN WITH THE ALABASTER JAR you won't find very much new material in THE TAROT TRUMPS AND THE HOLY GRAIL. TT is a synopsis of the Tarot material found in her earlier book and not nearly as good because she does not link the Tarot cards to paper watermarks, fairy tales, and other material as she did in her earlier book.
Starbird suggests the Tarot cards were used as an `Ars memoria' or a technique for creating mental images that allow one to store and recall information. Thus used, the cards would have proved invaluable for relaying `heretical' information in a sub rosa fashion in a climate where "thinking outside the box" got one burned at the stake. The notion the Tarot cards were used as memory devices for transmitting verboten information is not new. For example, Cynthia Giles makes a similar point regarding a possible hidden link between Gnostic material and the Tarot cards in her book THE TAROT published in 1991.
However, Starbird specifically links the Tarot cards with the notion that Mary Magdalen was the "holy grail" who carried Jesus' child (as well as the founder of the "church of love"). Furthermore, she suggests the Tarot cards can only be seen as an `Ars memoria' for the Grail story and have nothing to do with gypsies, Egypt, or India.
Starbird's argument for the exclusivity of the Grail-Tarot connection hinges on the date of the first appearance of the so-called Charles VI or Gringonneur deck which she links to the Grail story. Starbird suggests that if the Charles VI deck dates from the end of the 14th century it had to have been created before the arrival of the gypsies who are thought to have arrived in Europe in the 15th century. (Cynthia Giles suggests the Charles VI deck first surfaced at the end of the 15th century which means they "arrived" about the same time as the gypsies. Joseph Campbell suggests the earliest date of the cards as 1392 CE. However, Campbell also suggests the Tarot cards carry archetypical symbols that can be linked to many `religious' systems and/or works of art).
The clothing of the figures in several of the Charles VI cards such as "The Lovers" became popular at the end of the 15th century which would support Giles dating of the deck, but Starbird suggests the Charles VI cards might have been "updated" with "modern" clothing in a later edition.
I enjoyed reading Starbird's suppositions and comparing them with similar proposals by other Tarot writers. However, I don't think she has proved her point in this book. She presents a much more compelling case in the WOMAN WITH THE ALABASTER JAR.