De Morgan's laws are indispensable in digital electronics. The laws outlined by him are simple to understand, yet transformed the Boolean algebra in
a dramatic way.
A + B = A.B
A.B = A + B
Now try the following with a circuit and a truth
Maths is challenging; so is finding the right book. K A Stroud, in this book, cleverly managed to make all the major topics crystal clear with plenty of examples; popularity of the book speak for itself - 7th edition in print.