​A Theory of Dreaming will be released on July 29, 2025. It is the sequel to A Study in Drowning, and the conclusion to the duology. 

The Fairy King has been defeated. Effy and Preston returned from Hiraeth to share the truth about the beloved story Angharad, earning Effy a hard-won place as the literature college's first female student. In the stories that raised Effy far more surely than her parents, this would be the happily ever after. 

But the burgeoning war between Argant and Llyr is at odds with Effy's peaceful dream. Preston is branded as a liar and sabouter for his efforts to discredit Myrddin; Effy is hated enough just for being the girl who called a national epic into question. In the past, times like these are when Effy retreated into the dark solace of the Fairy King... but she can't escape the real world anymore through magic. 

Instead, it's Preston who finds his dreams drawn into an underwater castle ringing with the bells that have haunted him since leaving Hiraeth... a world in which he is the king. 

I read and loved A Study in Drowning last year, and so I jumped at the chance to review an advance copy of the sequel. Still, I admit I had my misgivings. A Study in Drowning's magic lay in its ethereal, uncanny tone; I wasn't sure if a sequel could possibly replicate that in a way that felt anything other than contrived. Ava Reid, however, is a far too skilled writer than that. A Theory of Dreaming is very different from the first book, but that's as it should be; while still straddling the real and unknown, this book anchors itself more in the present, focusing on the aftermath and consequences of earlier events. It also places its focus on Preston rather than Effy, though it largely splits page time between their points of view, and Preston's very different voice and background shines through. 
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In a word: gorgeous. A Theory of Dreaming is a romance, and yet far more than that; it is a war story, but without dramatic battles or conflicts; it’s about the remaking of a country, but no revolution is ever staged. As a reader who’s long wished for more character-driven high fantasy books whose driving force is personal stakes over apocalyptic consequences, this book was a gentle breath of air featuring characters and a setting I’d already fallen in love with. This incredibly rich, nuanced, and thoughtful story that delves into the story of after and the story of now, allowing Effy and Preston’s characters to truly flower. Reid’s writing is, as always, beautiful, and her ability to effortlessly weave together dreams, belief, mental health, and strong relationships in this book was truly amazing. 

My only real complaint with this book was not truly the content of the book itself, but with the lack of content warnings. This book is incredibly focused on misogyny, xenophobia, grief, and mental health, as well as containing an on-page suicide attempt. If any of these topics are even remotely triggering to you, I encourage you to check out my Goodreads review, where I’ve done my best to include a more thorough summary of these triggers under the spoiler functionality. 

Overall, I highly recommend A Theory of Dreaming to readers ages fourteen and up looking for a complex and thought-provoking sequel that truly couldn’t have been more satisfying. 

Thank you to NetGalley and HarperCollins for providing a review copy in exchange for an honest review! All opinions are my own.