Popularity is hard to define. The adoption rate is still very low among the general population, but public awareness that 3D printing exists is high and rising.
There have been several books published about DIY 3D printing (there's even a 3D Printing for Dummies). If I had to recommend one, it would be "Getting Started with RepRap: 3D Printing on Your Desktop" by Josef Prusa. Prusa is well-respected in the DIY 3D printing community, and unlike many authors in the space, he wrote his book about understanding the process rather than about the state of the art. As far as building your own machine, you'll want to stick with the internet – the current plans and best practices for that have been moving much too quickly for books to keep up. Your best resource is going to be the RepRap website and forums, and of course Google. If you want to keep up with the latest news on 3D printing, 3Ders and 3D Printing Industry are two of the best sites to follow.