Spoiler Alert! If you haven't read the fourth "Twilight" book -- and plan to -- this story is going to ruin your life forever. You sure wanna go on? Here we go...

Turns out Stephenie Meyer, the woman behind the Twilight series, isn't the only person to write about sexy vampires -- 'cause she's being accused of ripping off the storyline for her fourth ultra-successful book by a less famous, less rich author.

A woman named Jordan Scott fired off a cease and desist letter to the publisher of "Breaking Dawn" -- the fourth book in the series -- claiming the Twilight tale contains a "striking and substantial similarity" to Scott's book, "The Nocturne."

In her extremely detailed letter, Scott claims her book was published in 2006 -- two years before "Breaking Dawn" -- and it's no coincidence that many of the scenes are almost identical. Such as...

-- Both books contain a post-wedding sex scene

-- Both books contain a scene about a woman who's sick because she's carrying a child with "evil powers"

-- Both books contain a scene with the death of the main character's wife

And according to Scott, the dialogue in all of these scenes -- and more -- is extremely similar.

But Meyer's rep is calling BS -- telling TMZ, "The claim that 'Breaking Dawn' by Stephenie Meyer somehow infringes on an alleged book by someone named Jordan Scott is completely without merit. Neither Stephenie Meyer nor her representatives had any knowledge of this writer or her supposed book prior to this claim."

So, the million dollar question ...