• Amazon's "Lord of the Rings" spinoff, "The Rings of Power," launched on Prime Video September 1.

• The company has reportedly spent nearly $1 billion developing the streaming video series.

• The original Tolkien series has a rabid fan base. Upsetting them could hurt Amazon.

Amazon's $1 billion bet on its new "Lord of the Rings" streaming TV series is falling flat with initial audiences, posing risks for Amazon Studios and the company's Prime membership program.

Though critics have praised the series' scope and ambition, "The Rings of Power" has rankled with audiences, who gave the show a 39% rating on Rotten Tomatoes. (By contrast, Peter Jackson's early 2000s Lord of the Rings trilogy earned audience scores of between 86-95% on Rotten Tomatoes.) Even on Amazon-owned IMDb, audiences rated "The Rings of Power" an anemic 6.8/10.

HBO's "House of the Dragon," released last month, is performing much better. It has an 8.8/10 rating in IMDb and an 84% audience score on Rotten Tomatoes. For each show's three-day post-debut window, "House of the Dragon" attracted 51% more viewers than "Rings of Power," according to Whip Media data reported by TheWrap. The publication also looked at data from Samba TV, which tracks viewership through connected TVs in the US. That told a similar story: 3.1 million households watched the first two episodes of "Rings of Fire" in the first three days, while 4.8 million watched the HBO premier in the same window.

Counterintuitively, The Lord of the Rings' rabid fan base, including those obsessed with J.R.R. Tolkien's original books, may be to blame for Amazon's challenges.

"It will be impossible for Amazon to please the millions of Tolkien fans, despite the enormous budget for the series," Tom Forte, an analyst for investment firm D.A. Davidson wrote in a recent note titled "Jar Jar Binks Ruined My Adulthood" that drew comparisons between "The Rings of Power" and "Star Wars" fans' outrage over the 1999 movie "The Phantom Menace."