The clamshell iBook was larger than a Powerbook due to its round shape. Due to the rubberized edges and the rounded polycarbonate housing, the iBook should be able to withstand the high stresses of everyday school and study life.
Apple also tried to debunk the weight argument - the clamshell still fared well compared to Windows notebooks. Nevertheless, some made fun of the "bulky" iBook, as the image below with a little girl satirically underlines.
With the second iBook generation, Apple not only brought about a complete design change, but also made the iBook smaller, lighter and even cheaper - unfortunately at the expense of quality.