Authors may be "language pros" but the content can use more proof reading. One (trivial) example:

> Kanji are ideograms imported lock, stock, and barrel from __mainland Asia__ into Japan over hundreds of years, starting around the 5th century, followed by Buddhism in the 6th century.

"mainland Asia"? This makes me laugh. Technically not totally wrong, but, do people really say that? Won't people from India get offended? If someone (e.g, a child) googles "mainland Asia", the first result is Indochina. Did Japan import Chinese characters from Indochina in the 5th century? I believe a textbook should be clear, straightforward, and shouldn't obscure/blur facts.