Atom by Atom Against Cancer follows the hunt for drugs that rescue p53, the tumour suppressor protein mutated in more than half of human cancers. Starting from first principles in molecular mechanics and thermodynamics, the book builds the full computational drug discovery pipeline: force fields, solvation models, molecular dynamics, docking and scoring, free-energy calculations, virtual screening and ADMET prediction. Every method is taught through its application to the p53-MDM2 interaction, the most studied protein-protein interaction in oncology drug design. Written for scientists, students and professionals entering computational chemistry or cancer drug discovery, it combines rigorous theory with practical guidance on how these methods are actually used.