The most famous Dungeons & Dragons character has a novel that has never been released, as it was shelved over twenty years ago. There are a number of popular D&D characters, but Drizzt Do'Urden is easily the most iconic of them all.
Drizzt is a drow elf Ranger who resides in the Forgotten Realms campaign setting. The drow are hated throughout the Forgotten Realms, as they worship the even goddess Lolth and perform horrific acts in her name. Drizzt eschewed the evil ways of his people and fled the Underdark in search of a new life on the surface world, but there he faced prejudice at every turn. He debuted as a side character in the Icewind Dale trilogy, but it quickly became apparent that he was the star of the show, and the series shifted focus, becoming known as The Legend of Drizzt.
Drizzt was created in '88 by R.A. Salvatore, and he still pens The Legend of Drizzt novels to this day. All told, there are nearly 40 novels in the long-running series, but Salvatore once briefly stepped away and another writer was brought in to pen an ill-fated manuscript that remains lost (at least for now).
The Lost Shores Of Dusk
The D&D license was once owned by a company called TSR. After writing Passage to Dawn in '96, Salvatore stepped away from the series. The D&D magazines at the time started advertising a new Drizzt book, called Shores of Dusk. According to promotional material released about the book (via. Candlekeep), Shores of Dusk followed Drizzt as he returned to the Underdark and encountered drow that did not belong to his homeland. This book was written by an author named Mark Anthony, who discussed Shores of Dusk in a post that has been archived on Candlekeep. According to Anthony, he was brought in after Salvatore had a falling out with TSR. Shores of Dusk was completed, but was canceled shortly before it was meant to be published. This was because TSR was bought by Wizards of the Coast (the company that still owns D&D) and Salvatore returned to the series.
Shores of Dusk remains unpublished to this day, and it has become an infamous piece of lost D&D media. There's always a chance that it could finally be published as a non-canon story. The growing popularity of Dungeons & Dragons, coupled with Drizzt's starring role in Dungeons & Dragons Dark Alliance, could lead to Shores of Dusk seeing the light of day in the future.
Source: Candlekeep, (2)