Many of you have probably heard of bitcoin, the private digital currency that some mainstream merchants are now accepting. (Rand Paul recently became the first presidential candidate to accept donations in bitcoin.)

Bitcoin was developed by a software programmer who used the pseudonym Satoshi Nakamoto. It is built on cryptography software known as the blockchain, which both issues the currency and authenticates transactions using it.

If you haven’t heard of bitcoin or you don’t know much about it, I strongly recommend an interesting, informative new book : The Age of Cryptocurrency: How Bitcoin and Digital Money are Challenging the Global Economic Order, by Paul Vigna and Michael J. Casey.

Vigna and Casey are reporters for the Wall Street Journal. I think they're a little too optimistic about the future of digital currency, but their book is an excellent non-technical introduction to the bitcoin phenomenon and the blockchain software that underlies it. The book isn’t limited to bitcoin; Vigna and Casey talk about other digital currency. They also discuss other potential applications for the blockchain software, such as gambling, self-enforcing “smart” contracts, and currency exchange.

The book’s discussion of regulatory issues is limited. If you’re looking for a discussion of the legal issues, I suggest you look elsewhere. But the book is a very good introduction to digital currency and how it works.