The two hardcover box-set descriptions cover the first eight books split across two sets: one contains books 1–4 and the other contains books 5–8.
The listings include English-language editions and at least one Spanish-language hardcover edition.
Individual books are typically about 8.0–8.6 inches tall and weigh roughly 0.6–1.0 pound. Multi-book box-set packaging is larger and heavier; one example box measures about 8.5 x 5.91 x 3.46 inches and weighs about 3.65 pounds.
Most listings recommend these books for readers around 8–12 years old. A few list 9–12, and one box-set description notes suitability for 7–12-year-old readers.