This appears to be a condensed version of the booklet titled, Eastward Through the Storied Northwest, which NP published from about 1903 through at least the mid-1910s. While that older booklet attempted to entice Californians to make their journeys to the east via Northern Pacific, and thus extolled the virtues of the Shasta Route, this one focuses exclusively on the NP route. It also describes the route from east to west, while the Eastward booklet went from west to east.
The waterfall on the front cover looks like Wahkeena Falls in the Columbia River Gorge; the back cover shows an interior view of the late lamented Mitchell Point Tunnel on the old Columbia River Highway. Like the Eastward booklet, NP published annual editions of The Storied Northwest. I scanned this 1922 version owned by the Spokane Public Library and I’ll post later editions of this booklet in the next few days.