Here is a quote from that book:
When we walk, we receive constant feedback from our leg muscles and feet
such as stretch, tension, and load, in addition to having tilt and balance information
present from our inner ear. Remove this physical feedback information
and remove any visual clues, and it becomes much harder to walk. Imagine
how much harder, if not impossible, it would be to learn how to walk without
This lack of feedback is a dilemma for robotics. It is possible to program a
bipedal walker robot to walk without feedback and a sense of balance. To do so,
exact position control and movements are measured for each leg servomotor
action, each action sequence is programmed into the microcontroller, the program
is initiated, and the sequence repeated to achieve a walking gait.
So it is basically a sequence of repeated movement to make a legged robot walk or do anything else. A lot of work is in those sequences, but after they are done, the robot can move easily.
But to be a real balancing bipedal robot, it has to have inertial sensory feedback and all sequences need to be adjustable by some factor depending on the sensory input.
So, it can be easy or difficult, depending on your objectives. You may want to check out biped kits then add your stuff to them.