If Eden the TV series was based on a book, the book could be older, but it isn't.
It's also possible, but not likely, and not the case here, that a TV show could be a sensation long before the first episode comes out. I can't think of a time when this happened except for a prequel or sequel like Better Call Saul, where it was much awaited, but I'm sure there are instances of that occurring.
Edit: from another comment, there's this, which came out in 1997 but isn't mentioned in the Wikipedia article for the TV series so I'm not sure it's related: https://en.m.wikipedia.org/wiki/Eden:_It%27s_an_Endless_Worl... There is a Manga mentioned in the article for the TV series but it came out the same year as the TV show.
It's also possible, but not likely, and not the case here, that a TV show could be a sensation long before the first episode comes out. I can't think of a time when this happened except for a prequel or sequel like Better Call Saul, where it was much awaited, but I'm sure there are instances of that occurring.
Edit: from another comment, there's this, which came out in 1997 but isn't mentioned in the Wikipedia article for the TV series so I'm not sure it's related: https://en.m.wikipedia.org/wiki/Eden:_It%27s_an_Endless_Worl... There is a Manga mentioned in the article for the TV series but it came out the same year as the TV show.