A digital electronics book could be paired with it for exercises. Or heck build your own microcontroller or something.
A similar method is to instead of using a game to simulate circuits in software, use an FPGA to simulate a circuit in hardware. A cool book I've used to here, http://www.amazon.com/FPGA-Prototyping-VHDL-Examples-Spartan...
It will take you step by step from creating simple shift registers to displaying an image over VGA (which you implement yourself).
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