Despite losing a high-profile copyright infringement lawsuit against Harry Potter author J.K. Rowling, Steven Vander Ark is moving forward with publication of his unauthorized encyclopedia to her blockbuster series.

RDR Books will publish The Lexicon: An Unauthorized Guide to Harry Potter Fiction and Related Materials on Jan. 12, Vander Ark announced Friday at a Michigan bookstore.

The book is billed as a print version of the encyclopedic Potter website Vander Ark launched in the late 1990s.

Both he and his publisher have emphasized that the original book has been revised to reflect a trial judge's ruling earlier this year.

"We learned a lot at the trial about what was acceptable, what would follow the fair use guidelines," said the 50-year-old Vander Ark, a former school librarian.

"That was not clear before. There was no law on the books that made it clear what was acceptable and what wasn't," he added, saying he spent five or six months revising his book — originally slated for release in November 2007.

"Coming out of the trial, I had a much better idea of what should go into the book."

Rowling filed suit to block publication

At one time, Rowling praised Vander Ark's site for being so comprehensive in details from her novels, and the two had a warm relationship.

However, in fall 2007, the Scottish author launched a lawsuit to block RDR Books from publishing Vander Ark's encyclopedia. During court testimony last April, she fought back tears when discussing how her writing career had "saved" her sanity and pulled her out of a life of poverty.

Vander Ark also became emotional on the stand when he discussed how the trial had alienated him from the wider Potter community of fans.

In September, a judge ultimately sided with Rowling and against the publication of Vander Ark's book, ruling the encyclopedia would cause her "irreparable harm" as an author because it appropriated too much of her writing, despite being pitched as a reference tome for the widely read boy-wizard series.

RDR Books publisher Roger Rapoport emphasized on Friday that the new version includes "a lot more critical commentary, which means more analysis."

With files from the Associated Press