Understanding the distribution of income and wealth in an economy has been a classic problem in economics for the last hundred years. Apart from the rapidly decaying number density of people with their income crossing over to a robust power law for the very rich, known as the Pareto power-law, after Vilfredo Pareto. With the availability of accurate data from finance/income-tax departments of various countries, several robust features of the income distribution have been established. The book will report on the major models developed mainly by the (econo-) physicists over the last decade. Almost all the major physicists and economists involved in these studies will review their latest work and the associated developments. Physics models, in particular the gas models for markets will be extensively utilised and discussed. Apart from simulation studies and their comparison with the latest observed data, major analytical developments will be discussed.