I'd actually rate this a 3.5. I really enjoy this series and the related ones by Iris Johansen. That said, I would strongly recommend beginning at the start of the series. This is the 6th book, and by far the least standalone of the series. I rated it lower than the other Kendra books because this one got a bit choppy at times, ventured more into the romance btw Kendra and Lynch and less into Kendra's skills.

Kendra Michaels was born blind but had a miraculous surgery to correct her vision in her early 20's. Spurred on by her no-nonsense mother, relying upon and developing her other senses while growing up, she learned to recognize clues to her surroundings. Once she gained her vision she found she was a real help to law enforcement, finding clues others couldn't using her other senses.