There and Back Again: A Hobbit's Holiday

There and Back Again was a book written by Bilbo Baggins recounting his adventures with Thorin and Company and the quest to reclaim the Dwarf-realm of Erebor. Conceived as his memoirs, the book was begun by Bilbo upon his return to Bag End but not completed until his retirement in Rivendell.
The diary contained the story of Bilbo's finding of the One Ring as he originally told it: thus, Gollum willingly gives the One Ring to Bilbo, and there is no trace of the Ring's hold over Gollum, something that he never corrected, even when the truth was known.
Only to Frodo Baggins had he shown his journal, as much as he had written (and only he knew about his secret magic ring) and also Merry Brandybuck who took a peek secretly.
Bilbo kept the diary, along with a bundle of notes and papers wrapped in old cloths, in a strongbox in his study. He took these with him to Rivendell in T.A. 3001. In T.A. 3019 Frodo brought it back to the Shire (along with three volumes bound in red leather, a parting gift from Bilbo). During T.A. 3020-3021 he nearly filled the diary's pages adding his own memoirs of the War: The Downfall of the Lord of the Rings and the Return of the King.
Annexed to it later were the additional three large volumes of historical and cultural writings, the Translations from the Elvish. Bound together in a red case with a fifth volume added later, the volumes became known as the Red Book of Westmarch, the primary source for the War of the Ring and other matters of the late Third Age. The first volume containing Bilbo's journals however was copied most by the record-keepers.
A version of There and Back Again translated from its native language of Westron is said to be the basis for the modern novel known as The Hobbit.