I really loved Innocent Traitor, when Weir wrote her first historical fiction novel, but I found Captive Queen to be a bit of a drag, so it took me a while to get to this book and off my to-read list. 
 The book is told from two perspectives in two different, yet similar time periods. Both are named Katherine, but one is the sister of Lady Jane Grey, and the other is the illegitimate daughter of the infamous Richard III. I feel a little mislead by the synopsis, as it definitely refers to the story concerning the lost Princes in the Tower, so I thought part of the story would be their point of view, but their characters never really came up. I also found the resolution of the whole affair slightly unsatisfying, but that's also true of the historical story. 
 Until about 2/3 of the way through the book, I kept forgetting which Katherine was Katherine, and which one was Kate...until I told myself that Kate was the "baseborn" one and she gets the less classy name. 
 As is usual in these similarly structured books, I tend to gravitate towards one storyline or POV than the other. In this case, I definitely preferred reading Katherine Grey's timeline, partially because I kept waiting for it to get to the point where Jane was queen, and then imprisoned. Also, I found Kate's constant defending of her father and shunning her step mother for daring to question him really, really annoying. Katherine also veered towards the annoying, especially in the later time when she allowed herself to be used by the Spanish and was rather wishy-washy about everything. 
 These are the things that stuck with me the most while reading, but I did really enjoy this novel, and it's one of the few full-length novels that I've been able to finish in a while, so I take that as a positive on the read-ability scale.