Story from Middle-earth about the events of "The Lord of the Rings" being a lie

Question

In the early 2010s, I read a book about a group of adventurers in Middle-earth who retraced the steps of the Fellowship of the Ring and Frodo, only to gradually learn that the history of the Ring and the Ring Wars were mere lies and propaganda concocted by elves and Gandalf.

I do not remember the specific nature of the ruse or the reason for it (probably to keep the Ring), and that is why I want to find the book and read it again.

Here are the details I remember:

• The Ring wasn't destroyed, and Gollum didn't die at Mount Doom. Instead, he was a disguised elf by the name of Gil-gamesh (because all elf names start with "G"). He injured himself in the mountain. Over the years, he became disgruntled and had zero regrets about spilling the beans to the party.

• The party of adventurers included a dwarven female who fell in love with Gil-gamesh. They carelessly engaged in a physical relationship because they believed elves and dwarfs couldn't have children, which proved to be another falsehood spread by elves.

• Bilbo was in on the ruse, and the story of "The Unexpected Journey" was made up in order to persuade Frodo to do the dirty work.

• Moria was much smaller than the Fellowship of the Ring believed, but Gandalf deceived them by leading them in circles.

• Sauron was disposed of by an elite commando unit of elves; the destruction of the Ring was not necessary for his demise.

I read the book in Czech, but it might have been a translation... or not.

The book cover was beige/light brown with runes.

Answer 1

You're probably thinking of Kirill Eskov's The Last Ringbearer, a Russian book that re-tells the story of LoTR from the point of view of Mordor.

From Wikipedia:

Eskov bases his novel on the premise that the Tolkien account is a "history written by the victors". Mordor is home to an "amazing city of alchemists and poets, mechanics and astronomers, philosophers and physicians, the heart of the only civilization in Middle-earth to bet on rational knowledge and bravely pitch its barely adolescent technology against ancient magic", posing a threat to the war-mongering faction represented by Gandalf (whose attitude is described by Saruman as "crafting the Final Solution to the Mordorian problem") and the Elves.

Answer 2

So I found the book by randomly browsing local used books shop (they had several copies)

It is Tajemství Morie by Vladimír Šlechta or The Secret of Moria in English.

In my knowledge the book was never translated from Czech. Which is probably no surprise, since it is not very good.

Vladimír Šlechta is one of the most beloved Czech fantasy authors. He was one of the writers that jumped to satisfy the hunger for fantasy that existed in Czechoslovak literature after the fall of communisms. Mind you the first Czech translation of Lord of Rings was published in 1990, because it was prohibited under communist government. (Translation existed, but was spread in samizdat form). The 90's were wild in fantasy literature, with many, usually amateur authors filling the hole, many of those works being experimental, bad or copycat, yet all were ravenously consumed.

Šlechta managed to find his own decent style and produced some quite good books, but from time to time this ozone of freeform, free-spirited experimentation can be felt even in his later works, which in combination with phenomenon we call "Czech humor" can be the recipe for disaster like The secret of Moria.