The Unbreakable Code

Bertram, Jennifer Chambliss. The Unbreakable Code
April 25th 2017 by Henry Holt and Co. (BYR) 
E ARC from Edelweiss Above the Treeline

After their adventures in the delightful The Book Scavenger, Emily and James are hot on the heels of a new mystery, this one involving things hidden underneath San Francisco and a code that may lead to fires breaking out! Mr. Quisling is somehow involved, but they can't quite figure out what's going on. Fires are breaking out all over town, and they seem to all be tied to a code from the 1800s that has never been broken. Using their love of code and a little help from the dispirited Garrison Griswold, can the intrepid pair solve the mystery before someone gets hurt?

N.B. I read this, loved it, and clean forgot to write the review for two weeks. Hard to remember details, which is why this sounds a bit lackluster. My fault, not the book's!

Strengths: The San Francisco setting and history are phenomenal, and the use of puzzles and codes will appeal to many readers. I love that Emily and James are good friends and work together well. The cover, along with the fast pacing and things catching on fire, makes this a great choice for both boys and girls. Brilliantly executed. The first book is always checked out from my library. 
Weaknesses: I personally don't like puzzles and codes, so I didn't get as much out of this as I could have. 
What I really think: Very excited to get this to my students, and can't wait for the next book!