The Mirror of Infinite Endings

The Mirror of Infinite Endings is a companion volume — the fourth entry in the Once Upon a Broken Heart series, published by Flatiron Books — set in the Magnificent North and centered on Jacks and Evangeline Fox. Where the preceding trilogy charted the tumultuous arc of their relationship, this installment finds them in an apparent happily-ever-after in the Hollow. The publisher's synopsis, as stated on us.macmillan.com, frames the premise with deliberate irony: "Everything here in the Hollow is wonderful and perfect. Nothing is going to go wrong. No one is keeping a secret... Except for maybe one." That single withheld secret becomes the engine of the narrative, promising consequences that could, the synopsis warns, "rewrite reality or alter history or change the ending of Jacks and Evangeline's story." Beyond its central plot, the book features cameos from fan-favorite characters drawn from across the series' wider world.

A defining feature of this companion is its visual component: more than twenty full-page illustrations by Lotusbubble are woven throughout the 256-page hardcover. The inclusion of an illustrator — Lotusbubble, credited separately from Garber — marks this installment as a distinct reading object from the preceding trilogy, closer in format to a deluxe or gift edition than a standard novel. For readers who have followed Jacks and Evangeline since the first book, the artwork represents a new layer of immersion in the world Garber has constructed. The publisher presents this illustrated format as a central selling point of the companion, positioning it as something to be experienced as much as read.

Stephanie Garber is, as documented across multiple retailer and publisher sources, the #1 New York Times and internationally bestselling author whose books have been translated into more than thirty languages. The Once Upon a Broken Heart series carries that same #1 New York Times bestselling designation. Blurbs collected on the publisher's page speak to the appeal of the earlier books: critics described Garber as enchanting readers "with exquisitely imagined worldbuilding and her trademark heady romance," while Kerri Maniscalco, herself a #1 New York Times bestselling author, called the first book "an unputdownable fairy tale where Garber's imagination sparkles like the magnificent North." Karen M. McManus, also a #1 New York Times bestselling author, praised it as "a dazzling mix of mystery, romance, and magic." These endorsements speak to the established pedigree The Mirror of Infinite Endings inherits. Barnes & Noble included it among its Best Young Adult Books of 2026.

The companion is explicitly designed for existing fans of the Once Upon a Broken Heart universe. Its premise presupposes familiarity with Jacks — the morally gray prince whose dynamic with Evangeline drives the series — and with the Magnificent North as a setting. Readers new to Garber's work would arrive without the emotional scaffolding the narrative relies on; the payoff of a "one secret" that threatens an established happily-ever-after lands differently when readers have watched that happiness hard-won across prior installments. Garber's YA fantasy romance audience — readers aged 13 to 18, per the publisher's recommended reading age, though the series has a well-documented adult readership as well — will find this the natural next step. Those seeking a self-contained entry point into Garber's worlds would be better served starting with the first Once Upon a Broken Heart book or the Caraval series.

At 256 pages in a hardcover format measuring 6.5 by 9.55 inches, The Mirror of Infinite Endings is physically substantial for a companion novella, with its heft owing partly to the full-page illustration program. Its September 2026 publication date from Flatiron Books places it as a planned, crafted addition to the series rather than a hasty supplement. For collectors of the series in hardcover, the illustrated format adds value as an artifact. For readers primarily interested in narrative momentum or a longer, denser reading experience on par with the trilogy's main installments, the companion structure — and the novella-length story within a 256-page illustrated package — should be weighed against expectations. As with any series companion, its emotional resonance is proportional to a reader's prior investment in these characters and this world.