The original series told the story of human Bella Swan who fell in love with vampire Edward Cullen, now the new book is set to tell the tale from Edward's perspective.
It comes 12 years after Meyer halted the writing on Midnight Sun after an unfinished manuscript was leaked on the internet in 2008.
In a video message on US talk show Good Morning America, Meyer said: “I am very excited to finally, finally announce the release of Midnight Sun on 4 August.
“It’s a crazy time right now and I wasn’t sure if this was the right time to put this book out, but some of you have been waiting for just so, so long. It didn’t seem fair to make you wait anymore.
“Sorry about the bad timing. Hopefully this book can be a distraction from the real world. I’m so excited to finally be able to share it with you.”
At the time of the leak, Meyer said: "I did not want my readers to experience Midnight Sun before it was completed, edited and published. I think it is important for everybody to understand that what happened was a huge violation of my rights as an author, not to mention me as a human being."
She went on to say the book would be postponed "indefinitely".
The original four books were turned into a five-film series starring Kristen Stewart and Robert Pattinson as Bella and Edward. The first instalment hit cinemas in 2008, with the finale released in 2012.
Meyer's announcement comes after a countdown clock appeared on her website in the days prior, hinting that she would be releasing new material.