The Medici Heresy

A Vatican Secret Archive Thriller - Book 12

When Father Michael Dominic uncovers a sealed Renaissance letter hidden deep within the Vatican Archives, he awakens a five-hundred-year-old secret buried by Pope Clement VII at the height of the Medici dynasty. Joined by investigative journalist Hana Sinclair, Michael follows a trail of clues through forgotten chapels, papal confessions, and ancient astronomical alignments, each step drawing them deeper into a mystery the Church once swore to silence. What begins as a scholarly puzzle quickly becomes a struggle for survival as shadowed forces—both inside and outside the Vatican—move to control or destroy what Clement left behind.

Their search reveals two extraordinary manuscripts: the Gospel of the Beloved, attributed to Mary Magdalene, and the Codex of Voices, a Renaissance record documenting the Church’s attempt to bury it forever. As Michael, Hana, and their Swiss Guard allies navigate the danger closing in around them, they confront a truth that challenges not doctrine but conscience: why some voices endure across centuries while others are violently erased. With each revelation, the line between faith and fear grows thinner, and the cost of honesty becomes terrifyingly clear.

Rich in historical detail and steeped in Vatican intrigue, The Medici Heresy weaves a modern thriller through one of the Church’s darkest chapters. From Medici Florence to the underground chambers beneath St. Peter’s Basilica, this novel is a gripping tale of courage, betrayal, and redemption—where the past refuses to stay buried and the future belongs to those brave enough to face it.

While part of the Vatican Secret Archive Thrillers series, The Medici Heresy is a standalone adventure that can be enjoyed by new readers and longtime fans alike.

 

December 2025

Select Reviews for The Medici Heresy

A pope who was controversial in history has a secret that could pull the Church in directions the Vatican may want to prevent at all costs!

First and foremost, a large thank you to Reedsy Discovery and Gary McAvoy for providing me with a copy of this publication, which allows me to provide you with an unbiased review.

Always a fan of Gary McAvoy and his work, I gladly accepted the latest in the Vatican Secret Archives series. Never one to shy away from history and obscure documents (some of which blur the lines between real and fictionally crafted), McAvoy delivers perhaps his strongest and most comprehensive thriller to date, which I was able to devour in short order. A random delivery to Father Michael Dominic opens up a centuries-long secret. This sealed Renaissance letter is not only the perfect addition to the Vatican Secret Archives, but explores something Pope Clement VII held as his most important secret. A member of the controversial Medici family, Pope Clement VII is known for controversial events, which leads Father Dominic to reach out to his fiancée, journalist Hana Sinclair. Through a series of letters with clues embedded within them, Father Dominic, Hana, and two Swiss Guards begin to reveal the secret Pope Clement VII held close to his heart. It’s soon clear that the secret surrounds a new and highly controversial Gospel, that of the Beloved. Its discovery could completely change the Church’s foundational beliefs and direction for the future.

While the hunt continues, a powerful man with ties to the Medicis seeks to nullify the secret to ensure the Church doesn’t face the embarrassment of the truth. Fuelled by a desire to know what actually happened and a passion to ensure the Church speaks for honest Christian sentiment, Father Dominic and Hana forge onwards, hoping they will not be stymied. Even when the Church is made aware, a distinct crossroads emerged about how the current pontiff ought to steer Church doctrine. A stunning thriller that keeps Gary McAvoy at the centre of the fictional revelations of Church truths and the desire to share it with series fans!

Gary McAvoy has been my go-to author for both entertaining and educational novels related to Church history and secrets. He sharpens my keen interest in religious and secret documents held by the Vatican, which could drastically change the way Church dogma shape the views of the masses. With a strong foundation, McAvoy delivers a stunning exploration of these secrets, wrapped in history and controversy, keeping the reader on the journey with the protagonists. Themes of revelation and reexamination of the truth fuel the momentum of the piece, including a rethinking of how Jesus thought of his ministry and its extension past his own time in this world. Ideas of Church reactions to documents like the Gospel of the Beloved and Codex of Voices send the novel into a second journey that could derail centuries of messaging Vatican officials have made clear to Church followers. McAvoy almost wrote two separate stories here, as he sought not only to create a mystery to solve, but also how the Church’s reaction might take things down a new and awkward path when new revelations are permitted to see the light of day. Chapters push things along and keep the reader needing the flip pages well into the night to get to the heart of the matter.

Series fans will know how important characters are to McAvoy, developing a continuity that spans the entire collection. Father Michael Dominic and Hana Sinclair serve as central characters whose actions help drive the story forward. There is little time to waste as these two reveal truths that many would likely not want shared, but do so with an innocence of truth, rather than a means of trying to tear down Church doctrine. A handful of supporting characters and a key antagonist help contrast throughout the story, while never fully revealing what is happening until the moment arises. McAvoy is able to weave his many characters together to create the largest impact for series fans to enjoy.

McAvoy never shies away from controversy and surprise, which he presents with plot points embedded into the larger story. They are perfectly placed to keep unpredictable moments present and the twists plentiful, which has been a theme of the Vatican Secret Archives series from the start. Gary McAvoy has long wanted this series to thrive on mixing fact and fiction, keeping his reader hooked with questions that cannot easily be answers. I have compared him to a Steve Berry or Dan Brown in the past, which remains a firm belief of mine. While some might say this book could be read as a stand-alone, it would be a great disservice for the reader to miss out on the fruitful developments this entire series has to offer. Beginning with the first novel provides a great foundational genesis and ensures the reader does not miss any of the nuances that emerge with later piece in the collection. I cannot wait to see where things are headed or how Gary McAvoy outdoes himself once again.

Kudos, Mr. McAvoy, for the most intense and controversial story in the series to date.

REVIEWED BY

I love to read and review all sorts of books. My passion is crime and thrillers, but there are so many other genres that pique my attention. While I am not a full-time reader, I try to dedicate as much time to my passion as possible, as can be seen on my blog and Goodreads.