In the Middle Kingdom, the Pharaohs no longer look so serious and strong; now they look more boyish and eager, less like gods and more like people.
But they still keep many of the characteristics of Old Kingdom sculpture: they are still carved from granite, and they still face strictly forwards. Sculptors continued to have trouble making their statues stand up unless they had masses of stone between their legs, or sat stiffly on stone blocks with their hands on their laps.
Bibliography and further reading about Egyptian sculpture:
Eyewitness: Ancient Egypt, by George Hart. Easy reading.
Ancient Egyptian Art, by Susie Hodge (1998). Shows kids how Egyptian art relates to Egyptian religion and culture.
Hands-On Ancient People, Volume 1: Art Activities about Mesopotamia, Egypt, and Islam,by Yvonne Merrill and Mary Simpson. Art projects for kids, though the directions are really aimed at teachers or parents.
The Art and Architecture of Ancient Egypt (Yale University Press Pelican History of Art), by William Stevenson Smith and William Kelly Simpson (revised edition 1999). The standard for college courses.
Egyptian Art, by Cyril Aldred (1985). Another standard.