When Aldo Zelnick finds what looks like a diamond ring, he assumes it must be bogus, but after carelessly losing the ring he finds out that it was real and had a big reward for finding it, in a book featuring vocabulary starting with B.

Aldo, a ten-year old begins the fifth grade with his sketchbook.

When his school cafeteria eliminates sausage pizza and chocolate milk and incorporates healthier choices into its menu, Aldo Zelnick decides to fight back, recording it all in his illustrated journal.

"Just how humdrum is 10-year-old Aldo Zelnick's life right now? So humdrum that he sets out to measure which January day will be the most boring. So humdrum that Jack and Bee succeed in getting him to try some weird hobbies. So humdrum that his recurring Hawaii dream has become way more enticing than real life. So humdrum that even unathletic Aldo agrees to downhill ski with his superjock brother, Timothy -- and finds that hotdogging it on the slopes...

When they unearth a giant bone in a ditch, Aldo and Jack try to figure out the bone's origin and value, which takes them to the nearby university, the local pawn shop, a dinosaur dig site, and the Dinosaur National Monument.