The Demystified Series physics books by David McMahon are viewed as credible but not ideal for serious physics students. While "Relativity Demystified" provides useful tools for performing calculations in general relativity without technology, it falls short in theoretical depth, prompting readers to seek additional resources like Carrol's work. The series is criticized for containing numerous typos and errors, particularly in the Quantum Field Theory book, which reportedly has mistakes on nearly every page. Overall, while the books may be helpful for casual learners, they lack the rigor and accuracy needed for more advanced study in physics.