It's a simple but multi-faceted device.
In order to appreciate great concepts and inspiring designs you need to search and find examples that usually fit into specific problems/challenges that you have in a brief.
By looking at how other illustrators/artists work with zines/artists book formats you can begin to compare your strengths and weaknesses, and more importantly identify what it is you need to work on.
It could be things that deal with the idea itself, or the design aesthetic, or both:
a sense of contradictions in what's written to what's drawn
a play with scale and perception
a sequence of mishaps
a dictionary of what not to do
a shopping list
a set of trump cards
an instructional booklet
a treasure map
Consistency of visual language
Use of limited colour palettes
Combination of text and image
The use of foreground and background
The visual experience of unfolding the pages
The feel of the paper
The awesomeness of the drawn details
The mark making qualites
The sense of emotion of the colours/drawings
The list is Fudging endless