Powerful Mathematicians who changed the world: Agnes Meyer Driscoll. The Mystery Underground by Christa Jackson et al.

Rating: Needs Parent Supervision 

Reading Level: Early Elementary, Mid Elementary

There are a few potential hesitations:

• Stranger Danger. The main character is a young boy who meets a (kid) stranger and befriends them quickly. I love friendliness but they are too trusting too soon, exploring tunnels together and so on the same day they met.  I know it sounds awful but kids need to be aware of how other kids can be used as a lure.
• No Parental Supervision. Not telling a responsible adult before visiting tunnels on their own to investigate. 
• WWII, Japan. There is mention of history in WWII, including cracking Japanese codes. If your family is sensitive to the U.S.’s Treatment of Japanese Americans during the war, I still think this would be ok but you should know that there is mention of Japan as an opponent in that time.

This educational fiction has some brilliant characteristics:

• Educational Mathematics. Kids learn some cryptography and use some math to crack codes!
• Gentrification. Readers experience gentrification with a single-parent family
• Gap between rich & poor is described through the eyes of kids. Real life struggles like needing to watch younger siblings, differences in road conditions, home sizes, and other aspects of lifestyle and conditions. The exposure is real and honest.
• Kids are empowered to uncover corruption
• Kids grapple with imperfect parents
• Characters can be a mix of good & bad
• A green energy company is dumping toxic waste; shows that environmental innovation isn’t always cost-free.
• Honest history about lack of opportunities or respect for women in science. Kids may grapple with whether differences still exist.

Parents should know the authors have a clear agenda (if not several) so the gentrification, quality of life differences, and treatment of women in STEM are all strongly portrayed here.