I'm one of those people who will read a book and assume the stuff they keep referencing is backstory that doesn't need to be explicitly explained to be understood (eg. the "Bull(?) Hill incident") and go through the entire book without realizing that it is actually the second in a series.
I don't remember the name of the book, but this is literally what happened. I only have the second book in the series (which I believe is a trilogy) and I read through the whole thing and then realized after looking up the next book in the series that it was the second book. I never did get to reading the others but it was pretty good. Had some stuff about people being able to control portals and there being two worlds and weaving portals together to make stronger ones to connect them and people stealing others portals since you have a limited supply and also the portals heal you and are different colors and are harder to control when stolen and all that fun stuff. Pretty fun book. If I could tell you the name I would tell you to read it. I think the portals were called gates and the book had a yellow(?) cover? One moment let me look this up.
Aright the book is called The Gate Thief by Orson Scott Card and it's the second in the trilogy. The first is called the Lost Gate and the third is called the Gate Father. I've only read the gate thief. Pretty good book so I assume the others are too you should check them out.