One of my favorite, most impressive and ambitious books is the book "Wild" by Cheryl Strayed. It's an autobiography that shares her story of walking a portion of the Pacific Crest Trail (around 1,100 miles in total!). She was only 22 at the time of walking the trail and decided to take this journey after she experienced a tough divorce and the death of her mother. The book is a beautiful story of Cheryl's healing journey and the difficulties she successfully overcomes on the trail. I've read it several times and it touches me to my core every time.
"The Divine Comedy" a 14th-century Italian epic poem describes the author's journey through Hell, Purgatory, and Paradise, guided by the poet Virgil and his beloved Beatrice. It is renowned for its intricate allegorical structure, vivid imagery, and profound exploration of theological and philosophical concepts.
"Infinite Jest," written by David Foster Wallace, comes to mind. This work published in 1996 is known for its difficulty and ambition. "Infinite Jest" stands out due to the uniqueness of its narrative structure and length. The novel features a number of people and tales that regularly break apart and get intertwined with one another. The footnotes in the book provide information and context, and they are frequently longer than the text itself. In spite of its complexity, "Infinite Jest" has garnered praise for its comedic value, high level of intellect, and originality. The topics of addiction, entertainment, and the search for pleasure are delves into in this book.