I guess you could call this a mystery book for scientists. Sir Isaac Newton is the main character, & as I've heard it described elsewhere, he plays the Sherlock Holmes to his assistant Christopher Ellis's Watson. Written from Ellis's point of view (he was a real guy too!) the story is very well done & shows much of the inner workings of Newton's mind.
Newton has been put forth as the most intelligent human ever, since all later physics is based upon the firm foundation that Newton built. The main mystery of the book is the solving of a seemingly unsolvable code. The code has been found on the bodies of several dead guys discovered murdered in the Tower of London. And since the Mint was housed in the Tower, & since Newton was head of the Mint, he set out to figure out what was going on. There's a lot of great action to break up the intellectual stuff & some romance with Ellis thrown in for good measure.
I'm glad the book is written in Ellis's voice, since otherwise we'd be reading a bunch of scientific mumbo jumbo with a little bit of plot thrown in. As Ellis himself finds out when he tries to read some of Newton's much-lauded publications, he can't get through them awake. But that doesn't stop him from respecting & admiring the amazing brain that was Newton.