The folks at the Overview Bible Project received raw search data from BibleGateway.com to determine what the majority read and altogether avoid since the inception of the popular Bible tools website in 1993. 20 years of data and Bible searches now in the billions seems like a good sampling.
Surprised to be Left-off the Most Popular List: James. James may be looking down from heaven disappointed* but he can justify this by reminding himself his letter remains a go-to Bible study book with other people, but perhaps we are not necessarily looking for verses of his letter on a search engine or as part of our personal Bible study.
* - unlikely since he is in the presence of Jesus.
Surprised to be Left-off the Least Popular List: Leviticus. Moses surely thought included on this list would be his guidebook that includes how to deal with unseemly cold sores and which precious livestock you need to have sacrificed if you accidentally touch a dead fly. Rejoice my main man, Moses! I've still never heard anyone preach a sermon series from it, but Leviticus ain't no cellar-dwellar either.