Review of King's Cage-Victoria Aveyard

This is the third book in the Red queen series and the, I assume, final book in the series.  I must confess that I had a hard time finishing the book and put it down to read other books several times.  This book is so grim!  Mare Barrow, the lightning girl, is held prisoner by Maven Calore, who once loved her.  But, his love has turned into a torture as he manacles her with Silent Stone that not only dims her powers but is painful to the extreme.  He also humiliates her at every turn, even branding her, as she keeps hoping for rescue.  The final battle is thrilling but with great losses on both sides.  3 Elves - recommended for mature teens and adults