Too good to be true? Yup.
Go to the Author Publishing Terms and Conditions and you will find:
By submitting your Work to Autharium and accepting these Terms & Conditions, you grant to Autharium the exclusive right and licence to produce, publish, promote, market and sell your Work in any Digital Form (as defined in paragraph 1.4 below) in all languages throughout the world for the entire legal term of copyright (and any and all extensions, renewals and revivals of the term of copyright).
What is the legal term of copyright? The author's lifetime, plus seventy years. So by publishing a novel on Autharium, you hand over the worldwide digital rights, including film, games, apps [see edit below], and means of transmission yet to be invented, until seventy years after you die.
The site tries to fudge this by assuring you that The copyright in your work shall remain your property. Quite what good this will do you when you have ceded all rights to them they do not say. They do say:
Please note that your removal of your Work from sale in accordance with paragraph 13.1 above will not terminate this Agreement nor cause the exclusive digital publishing rights that you have granted to Autharium pursuant to paragraph 1 above to revert to you.
If you wish to sell your Work in any Digital Form through any other publisher, distributor or means then you will need to contact Autharium at email@example.com to agree transfer of the digital publishing rights to your Work.
So if you decide you will do better selling via Amazon's KDP, or are offered a six-figure deal from a publisher, or someone is interested in buying the film rights, you will have to persuade Autharium to release you from its contract. For a large sum of money, no doubt. Or you could decide the contract is so one-sided it may be unenforceable; in which case you face years of stressful and expensive litigation.
I think Autharium is playing a numbers game. Recruit enough writers to sign that contract, and the odds of one of them turning out to be the next E.L. James and making the site owners a fortune are really not bad at all.
Autharium? Avoid, and tell your friends.
N.B. For more information, see The Passive Voice, where I read this story.
EDIT: I've just had a long phone conversation with Simon Maylott, one of the founders of Autharium. He tells me that their contract does not cover film, games or app rights. He also defended the contract as being in line with traditional publishing contracts. The problem is, traditional publishing contracts are not generally fair to the author - read a lawyer's opinion here. I don't believe Autharium is consciously attempting to dupe the vulnerable, or that its owners are villains. But the legal term of copyright is a very long time, and who will be dealing with those contracts in thirty or forty years? Supposing Autharium is successful, and is bought out by someone less scrupulous? If the deal they offer is good, and their authors happy with it, their terms do not need to be so stringent.
EDIT 2: Having now looked at some books epublished by Autharium, I can say their proofreading, formatting and cover design do not strike me as being of a professional standard.