Please see the recipe LDA to classify documents and text into topics in Chapter 8, Unsupervised Clustering with Apache Spark 2.0 for a more detailed explanation of the LDA algorithm itself.
The following white paper from the Journal of Machine Learning Research (JMLR) provides a comprehensive treatment for those who would like to do an extensive analysis. It is a well written paper, and a person with a basic background in stat and math should be able to follow it without any problems.
Refer to the http://www.jmlr.org/papers/volume3/blei03a/blei03a.pdf link for more details of JMLR; an alternative link is https://www.cs.colorado.edu/~mozer/Teaching/syllabi/ProbabilisticModels/readings/BleiNgJordan2003.pdf.
