The two are not at all similar. Petzold's "Code" is good but is aimed at non-technical readers while "The Elements of Computing Systems" is more or less a text

The two are not at all similar. Petzold's "Code" is good but is aimed at non-technical readers while "The Elements of Computing Systems" is more or less a textbook that encapsulates a longitudinal slice of a 4-year computer engineering program, complete with exercises. It's really quite impressive in what it manages to cover (although the massive amount of material glossed over or omitted does make me wince).