Interstate was created as a book, which is its primary form, but it is also available as an ebook in iBooks format (readable on iOS devices and Macintosh computers running the Mavericks operating system). The electronic versions--ebook and on this site--are representations of the project rather than alternative versions. The physical book, which is much to be preferred, is available for its cost of production through Blurb at this link. The electronic version is available for free download here. 

For your convenience, and so that it may be viewed at a size closer to that of the physical book, the pages are reproduced below. Click on a page to enter "lightbox" mode.

The book's Introduction explains the project in detail, which can be read below or, in a more visually forgiving format, at this link.