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Publication Order of Tunnels Books
| Tunnels | (2007) | Hardcover  Paperback  Kindle |
| Deeper | (2008) | Hardcover  Paperback  Kindle |
| Freefall | (2009) | Hardcover  Paperback  Kindle |
| Closer | (2010) | Hardcover  Paperback  Kindle |
| Spiral | (2011) | Hardcover  Paperback  Kindle |
| Terminal | (2013) | Hardcover  Paperback  Kindle |