BB:

Board Books: toddlers, under a year to 3 years old (yo)

PB:

Young picture book: 2-5 yo

Picture book: 4-7 yo

Older picture book: 5-9 yo

Beginning reader: 5-8 yo

Chapter books:

Early chapter book: 6-9 yo

Chapter book: 7-10 yo

MG:

Middle grade: 8-12 yo

YA:

Young adult: 12-18 yo (pre-college)

NA:

New adults: 16-19 yo