Veteran actor Andy Serkis, known in part for playing Gollum in Peter Jackson’s The Lord of the Rings movie series, is set to return for another Middle-earth project, but it’s not a new film or TV series.

Serkis told Collider that he will narrate an upcoming audiobook version of J.R.R. Tolkien’s The Silmarillion. Serkis let this slip as part of a wider comment about his reaction to Amazon’s The Lord of the Rings: The Rings of Power. Serkis said he wanted and enjoyed the series, calling it “incredibly engaging.”

Serkis previously recorded the audiobook for The Lord of the Rings and The Hobbit, and he also read the appendices, from which The Rings of Power draws some of its material. In this comment specifically, Serkis revealed that he’s working on an audiobook version of The Silmarillion as well.

“Because I’d done an audiobook recording of The Lord of the Rings, and read the appendices, and had to read them out loud, I was quite clued up about where it was going to go, which was great, and it was really helpful because I’m going to be– don’t tell anybody–reading The Silmarillion, as well. So you heard this first,” he said.

It’s obviously still early days for Serkis’ The Silmarillion audiobook, so there is no word yet on when it’ll be released or any other details. The Silmarillion, which was first published in 1977 after Tolkien’s passing, digs deep into the history of Middle-earth and is known to be a very dense and challenging book to read.

Serkis currently stars on the Star Wars TV series Andor as the Imperial prisoner Kino Loy. It’s just the latest Star Wars role for Serkis, who previously played Supreme Leader Snoke in the new Star Wars series.

In other Lord of the Rings news, Warner Bros. Discovery recently confirmed it still has the rights to The Lord of the Rings movies following Embracer’s acquisition of Middle-earth Enterprises.