This supplement goes through some new roles and rules for travel. It does not cancel the existing rules for travel in a DnD 5e game, but enhances travel with some new roles and rules to make it more interesting. By any means, this is not a complicated full-on travel mechanics manual since that would be out of the purpose of this supplement.
The goal of this supplement is to make travel interesting again. Frist edition DnD was all about traveling and exploring. These rules aim to do that without making the game boring and take too long, since the rules are simple and easy to use. It is perfect for sandbox campaigns where travel and exploring matters and is an important aspect of the game, but also for quests and adventures that require you to travel from point A to point B. The travel between those points can prove challenging with enemies strolling and attacking the group to create setbacks to the party's advancement.
Why though?
Because in a fantasy setting, travel used to be (and still must be) a very important aspect of the whole story. The world is a real and dangerous place where all kinds of mosters and hazards lie in every corner of it. A simple description cannot cover the awsomeness of the world. Also, many popular books and films contain quests at the style "go from A to B and do this". So you know that travel is important.
It could be what's missing to fill in the blanks of your game, or to advance your game to the next level!
- from the publisher's blurb