Sister Siren Books

— home of the debut novel Moonstone Mountain —

“Hooked from the start, I sped through this book. The writing flows easily and is thoughtful and precise in its detail, making me feel like I was with Maggie every step of the way – starting with a wine night on a couch in London to a palace in Portugal that holds something deeper and perhaps darker to be revealed. The plot has thickened and the suspense already has me anxiously awaiting the sequel.”

— Angelina D.
“Full of stunning descriptions of the beautiful Portuguese sites and enough interpersonal intrigue that I couldn't put the book down. I feel like the characters are my own friends and I can't wait to see what happens next!”

— Meg A.
“It’s a joyful and heartfelt romantic mystery – Maggie is the friend you wish you had!”

— Kendall S.
“Book I has you constantly guessing where the story will take you. It’s an adventure that keeps getting better with each chapter.”

— Felicia C.

At the Moorish Monserrate Palace, hidden deep in the mountains of Sintra, Portugal, Sister Siren uncovered a story seeping through the cracks of time.

She could see it all around her — the lavish parties, the scandals, the Gatsby-esque frivolity.

Despite the palace standing empty for nearly 80 years — and likely devoid of any such parties in over a century — it seemed to her the veil between the past and the present had grown thin on that May day in 2024.

She could sense the ghostly presence of the family that once lived there, the echoes of their music and laughter lingering in every room. Their energy was still thick, as if they were calling out from the faded wallpaper, from beneath the glossy marble floor, from behind the dusty bookcases, and beyond the closed doors.

And the more she wandered the grounds and gardens, the more she needed to know…

what it had really been like at Monserrate Palace, one hundred years ago.

Explore the Story

So, she left Lisbon with a vision,

she researched,

and she wrote

of timing and its cost,

of love and loss,

and the power of letting go.

Moonstone Mountain

— a debut novel by Sister Siren —

Inspired by both fact and fiction, real places and imaginations, Moonstone Mountain is an immersive romantasy exploring love and loss, fate and choice — as one woman desperately searches for home in the midst of devastating change.

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Meet the Author: Sister Siren

A black-and-white photo of a woman with long hair, wearing a short-sleeved top with ruffled sleeves and white pants, standing outdoors with foliage in the background.

Sister Siren is the pen name for Olivia LeAnn O’Brien, author of Moonstone Mountain. Known for her TikTok presence (@sister.siren) as a professional life coach and content creator, she is now embarking on a new journey, fulfilling her childhood dream of becoming a novelist.

About the Author

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