I was a little lost at first. I borrowed the Kindle edition from my library, not realizing that Locked in Silence is the fifth book in a series. The prologue meant absolutely nothing to me, and then it took a while for me to figure out what it had to do with the rest of the book. Eventually I got it, and ended up enjoying the story for the most part.
The world building was a little lacking, however, I'm sure that is due to this being part of a well-established series and the author wanting (rightfully) not to repeat herself with every book. If I had been reading this series from the beginning, I'd be annoyed if she did a full explanation of what's going on in this world in every book. Sometimes you just can't win. Sorry, authors!
Silence and Vanya are both very likable. Silence's true identity (OR IS IT?) is handled so casually it's almost a throw-away, and really, I'm not sure it was even necessary to include. He was pretty interesting before that, and for a brief moment, all I could picture him as was(show spoiler)
which is not a good thing in my book. (I'm weird, I know. I just do not get the appeal.)
Anyway, a quick, easy, all-around enjoyable read.