How many books currently follow the book Eragon in the same series (2015)?

Eragon is the first novel in the Inheritance Cycle by Christopher Paolini. The Inheritance Cycle has four books in total. After Eragon is Eldest, Brisingr, and Inheritance. Thus, 3 books follow Eragon.

The first book in the series, Eragon, was originally self-published by Paolini in 2001, and subsequently re-published by Alfred A. Knopf Books for Young Readers on June 25, 2003. The second book in the series, Eldest, was published by Knopf on August 23, 2005. Both were New York Times bestsellers. The third book in the series, Brisingr, was published by Knopf on September 20, 2008. The fourth and final book in the series, Inheritance, was published by Knopf on November 8, 2011.