Dean Karlan is one of my favorite young economists and in April he will publish a popular economics book, co-authored with Jacob Appel. The subtitle is How a New Economics is Helping to Solve Global Poverty.
Consider the book an accessible account of "the new development economics," based on field experiments and randomized control trials. Much of the text focuses on micro-credit, where Karlan has done considerable work, but there is also material on public health, cell phones, and how to get parents to send their kids to school (pay them!).
Anyone interested in a readable treatment of the new development economics should pick up this book.