An egocentric writer translates a novel that details the impending torture of him and his family unless he figures out who wrote it and makes amends.

Sounds similar to "Stranger than Fiction". The difference being that the victim is fated to be murdered, not tortured. And the victim/protagonist is a really a nice guy, even for an IRS auditor; we, the audience, want him to live.

So, as Nir Shelter noted, why would the audience root for the egocentric writer? His family, yes, but since they seem like innocent victims of his own character flaw, it make him even less sympathetic.

The only bit that I am tripping over on is the last few words. They feel a bit like "and they all lived happily ever after". "Who wrote it and make a means" is to vague and lacks real action. Perhaps outline what motivate the original author, then it gives you something to resolve.

I like it. I recent saw a film about a priest that during confession is told he is going to be murder. The person in confession gives him 7 days (I think) to settle his affairs.

Is egocentric the best word to describe the writer. Nir immediately headed in a direction I didn't. I know some egocentric people that I could never describe as a prick. Unless the word is a good fit drop it till you find the perfect word.

Perhaps the writer is an innocent victim, the other author is obviously deranged.

There will be 2 kinds of sequences,
-the reality, with the writer, his job and his tentative to protect his family,
-the content of the novel, where we see what could happens (his family been tortured)

I think the writer will finally find that the murderer is himself, but I don't think you have to give any clues in the logline. Or he thinks to be the murderer but ... (surprise).

I think the problem with your MC is just the way you present him in the logline. In fact I can imagine a character who start as a selfish writer, then he SEE (in the novel) her family in danger (greater dangers... first someone spying on them, then kidnapping, the torturing etc) so the writer understand that he cares and that he need do do something to stop this (and become a better person).

I think the expression "make amends" is too vague.