My December book recommendation for that favorite tween in your life is Guts by Raina Telgemeier. Kids age 8-12 are the target audience, but I think it has a broader appeal. Telgemeier is a popular graphic novelist for kids and has previously written other books on stressful topics for that age range like Smile which addresses the awkwardness of getting braces.
Guts walks the reader through an autobiographical story describing how when Telgemeier was in fifth grade, she threw up, and then developed anxiety about getting sick. The author details how her parents took her to therapy and how she was able to work through her fears. The book also does a great job at destigmatizing going to therapy.
I would recommend this book to all kids, but particularly if your children struggle with anxious feelings and/or you are thinking of taking them to therapy. The idea of going to therapy can be super scary and intimidating for adults, let alone children. The novel normalizes the process in a fun way. The Telgemeier books are usually in high demand at the library and can be hard to find there, luckily, the book is fairly inexpensive. Pick up a copy today!