Charlie Thorne and the Last Equation by Stuart Gibbs

 Charlie Thorne is a 12 year-old-genius with an IQ over 200.  She is already in college, but often skips class out of boredom.  She is, rather dramatically, "recruited" by the CIA to help solve a 70 year mystery about an equation Einstein revealed right before his death that could bring prosperity or distruction to the whole world. As she joins a small elite group of agents on a quest that will lead them across the globe, she wonders if the secret Einstein so carefully hid would be safe in anyone's hands. 

Ok, this is my new recent favorite in the Kid's Lit category.  I have been a great fan of Stuart Gibbs for a while.  His action sequences are wonderfully written.  He adds thrills and humor in generous helpings.  What I like most, though, is the intelligence of both his plot and his characters.  Charlie is an interesting mix of adolesence and genius.  She sees through complicated issues quickly, but isn't above sticking her tongue out at someone. The other characters are nicely filled out as well.  As with his other books, Gibbs doesn't shy away from ethical questions, and doesn't give in to easy answers. Smart writing for smart kids.  (I just put the second in the series on hold :) (2020, 416 p)