The Judas Blossom is an historical fantasy novel that starts The Nightingale and The Falcon series, a reimagining of the Persian Empire story, written by Stephen Aryan, and published by Angry Robot Books. In this new series, we get immersed in the fights and political intrigue that surrounded the Mongol and Persian Empire during the Ilkhanate of Hulagu Khan, grandson of the famous Genghis Khan, whose expansionist ideas still last.

Taking place at the height of the said expansion, we have a character-driven story that follows four different POVs, each one with a different background: first of all, we have the own Hulagu, the general of the armies who using violence as the method it's expanding the Mongol empire through Persian lands; secondly, Temujin Khan, son of Hulagu, a complete disappointment for his father, but determined to live to his father ideas, getting enrolled into the army after his umpteenth failure. In addition to those POVs from the Khan family, Aryan decides to give one to Kokochin, the famous Blue Princess, a rather obscure historical character, the last of her tribe and that becomes one of the wives of Hulagu; and finally, we have Kalvon, a Persian rebel, aware that it's almost impossible to beat the Mongol Empire by the use of military force, decides to take the opportunity of joining as one of the assistants of Hulagu.

Those four POVs are masterfully woven into a compelling story by Aryan, who manages to portray a rather unknown historical period, bordering at many points the frontier between historical fiction and historical fantasy. And a rather dark historical portrait, I must say, as the author is not shy of showing the violence and the destruction that accompanied the Mongolian armies during their conquests.

Pacing is relatively slow, as a big part of the book is used to build solid foundations to create a big story over them. Despite this, I would say that it is a really interesting book to read, as even when building said bases, there is plenty of action and intrigue (especially during the research made by Temujin, and The Twelve inclusion).

I must add that worldbuilding is made with an exquisite tact for foreshadowing details that later will gain relevance, and the research behind the historical aspect of this book is one of his strengths. 
Fantastical aspects are marginal, in the style of some other low fantasy stories, such as Game of Thrones, despite I suspect it will become more important in the next books.

If you are looking for an excellent historical fantasy novel, The Judas Blossom is a great starting point. Stephen Aryan has written a marvelous story, and I, personally, can't wait for the second book in The Nightingale and The Falcon series.