Ramanujan occupies a unique place in analytic number theory: his formulas, identities and calculations are still amazing mathematicians three-quarters of a century after his death. Many of his discoveries seem to have appeared as if from the ether. His mentor and primary collaborator was G. H. Hardy. Here, Hardy collects 12 of his own lectures on topics stemming from Ramanujan's life and work. The topics include: partitions, hypergeometric series, Ramanujan's tau-function and round numbers.