The library is experimental as the functionality is not tested with hardware yet. The AD5231 is a single channel, 10 bit = 1024 step, SPI based potentiometer, the AD5235 is a dual channel version.
Developers, hobbyists and makers looking to learn more about communicating with I2C and SPI components, may be interested in a new teaching solution created by Daniel Hienzsch in the form of the I2C ...