If you've never spent a solid week on a couch reading a book, I highly recommend doing so at least once in your life.
A whole week? Even the biggest novels top out at around 1000 pages. The fattest single-volume mass-market paperback novels I have seen other people actually reading are King's _It_, Michener's _Hawaii_, Mitchell's _Gone With the Wind_, and Rand's _Atlas Shrugged_. Those might last the whole week, if you spent most of it napping.
That said, I recommend it be done on a sandy beach or on a hammock rather than the couch, and at least once per year, rather than once per lifetime.
For me, it was Stephen King's "The Stand" (1152 pages) when I was on summer break in high school. I fully admit it would be harder for me to schedule a stretch like that today.
Every form of media can do that. By pure numbers video games lead, but whether a type of media is immersive depends on an individual.