Short answers, pulled from the story.
Michael D. C. Drout served as chief editor. His co-editors were Douglas A. Anderson, Verlyn Flieger, Marjorie Burns, and Tom Shippey. Anderson and Flieger also worked with Drout on the journal Tolkien Studies.
The J. R. R. Tolkien Encyclopedia was published by Routledge in 2006. It runs to 720 pages and drew contributions from over 125 scholars across multiple countries.
Taylor & Francis acquired Routledge while the encyclopedia was in production and shut down the Routledge encyclopedia division. As part of the resulting disruption, all planned illustrations were dropped from the printed work, leaving the final volume with none despite Drout having gathered around a hundred.
The encyclopedia covers adaptations for cinema, stage, and television; characters; languages real and invented; Tolkien's biography; literary sources; monsters, peoples, objects, and places of Middle-earth; Tolkien's academic scholarship; theological and philosophical concepts; and critical history, among other themes.
Reviewers found the quality highly uneven. Kelley Wickham-Crowley wrote that entries ran "the gamut from masterful to pedestrian" and documented numerous errors in grammar, spelling, and bibliographic format. John Garth, writing in the Times Literary Supplement, said the encyclopedia "seethes with insight and opinion."
Carl Hostetter wrote the section covering all of Elvish linguistics in the J. R. R. Tolkien Encyclopedia. Reviewer David Bratman found it so much stronger than surrounding entries that he wished the entire work had been produced at the same level.