Some spoilers for Netflix's Dark ahead.
Even though Netflix's new German original series, Dark, is drawing some Stranger Things comparisons, there are a lot of important differences between the two shows. Though Dark has the same delightfully creepy sci-fi vibe that makes Stranger Things so bingeable, its complex plot shines under its own merit. One of the show's key characters is a watchmaker named H.G. Tannhaus, who builds a working time machine and then later writes a book about it, which a few characters are seen reading. So, is H.G. Tannhaus' A Journey Through Time from Dark a real book?
In the 1953 timeline, Winden's watchmaker receives the blueprints for the time machine mechanism from Claudia. It is only later in his life — presumably in the 1986 timeline — that he sits down to write A Journey Through Time, which we see Helge give to Claudia as a gift when she starts her new job at the nuclear plant in 1986. At some point during the writing of the book, we can assume that Tannhaus realizes that Winden is stuck in a time loop, because he starts cryptically telling people things like, "The past doesn't just influence the future, the future also influences the past," and "It's like the question of the chicken and the egg. We can no longer say which of the two came first. Everything is interconnected."
Since H.G. Tannhaus likely isn't a real person, we can safely assume that A Journey Through Time is not a actual book. However, just as the character of H.G. Tannhaus is likely based on a few key historical references, we can surmise, then, that A Journey Through Time is meant to remind us of a few actual works of literature.
One of those was written by H.G. Wells, who, in addition to sharing two initials with the clockmaker, also famously wrote a novella called The Time Machine, which follows a character simply named the Time Traveler who goes on occasionally harrowing adventures into the future and the past; he later disappears and his fate is left open-ended. Wells is commonly credited with coining the concept of a vessel called a time machine, which could allow for passage backwards and forwards through time.
A Journey Through Time is definitely not a published book that actually exists as a manual for time travel in real life. After all, there can't yet be a book about the subject or methods involved in actually traveling through time, because science has not actually figured this whole thing out just yet. However, there is a work of fiction not unlike that of H.G. Wells that deals with what might happen should time travel become possible. Time and Again by Jack Finney tells the tale of a 20th century fellow who is transported back to New York City in 1882. The whole thing treats time travel as a method of transportation or to carry messages between times, which us almost what it becomes in Dark. This book, along with Wells' The Time Machine, was named one of the Top 10 Time Travel books by Huffington Post.
By all accounts, the bespectacled and quirky H.G. Tannhaus is unfortunately not a real person and A Journey Through Time is sadly not a real manual for a working time machine, but he and his ideas certainly seem to have been inspired, at least partially, by some real figures who dabbled in the notions of time travel. Whether it's fiction or a nod to some real possibilities, the conversation surrounding time travel remains alive. If the subject even slightly interests you, Netflix's Dark, whose first season is now streaming, is a fascinating and thrilling ride to take.