Question: I'm working on an outline for a series of books. These books have an adventure plot line and I'm finding that the story goal of each individual book often seems to be simply "Getting from point A to point B." My protagonist has his own goals throughout the story, and I have an overarching story goal for the series, but arriving safely at each destination seems to be the main goal for my group of characters. Is that enough?
Honestly, it sounds like a rather thin goal.
I might ask why getting to a certain destination is important to the characters. What do they need to do at this destination? Why not stay where they are?
And there should be a consequence if they fail (other than not getting to the destination). In other words, the goal should be to avoid a bigger threat that is growing closer.
If you have a goal for the series, then it is worthwhile to consider each book to be an act in the overarching plot. And acts are not all the same.
For instance, let's take a typical adventure goal such as finding a certain treasure. Dramatica would call that a goal of "Obtaining."
In a four act (or four book) story, only one of the four will actually have an external plot concerned with Obtaining. The others will be concerned with Learning (getting information), Doing (e.g. traveling), and Understanding--not necessarily in that order. Giving each part a different concern makes the story more interesting.
Something else to consider...
Assuming each book is one act in the entire story, then the first act is the Setup, the second is the Complication, the third is the Move to a Crisis, and the fourth is the Move to Resolution.
(That would be a tetralogy. In a trilogy, acts two and three are combined in the middle book.)
(Of course, each of these four concerns can be broken into its own 4-part story arc, within separate books.)
The point is that, in addition to having a complete story, each book should make the reader hungry for the next -- to see what happens next in the overarching story arc -- until everything gets resolved in the last book.
That means there should be a progression -- a build in tension or a ticking off of accomplishments in order to build towards a crisis and ultimately to the achievement of the goal. And a progression implies that each act is different.
Best of luck.