I'm reading a book I won't name in which many of the secondary characters bother me. It's not that they aren't well-drawn. It's that I have no idea what they're doing in the book. I can easily imagine the book without them and their subplots. In fact, I've been getting impatient with them and their subplots, because our spending time there is only delaying the showdown that will be the centerpiece of the main plotline. (I know because I peeked ahead to see whether this book is worth finishing.)
This is a series, and I'm thinking maybe these secondary characters reappear in a future book, and that's why I don't fully understand their function now. And yet--part of me thinks there must have been a better way to do this. So far, these characters feel like filler. I seriously bogged down in this book, and it was only my loyalty to the main characters that made me look ahead to see if we eventually get back to the interesting stuff. And it's only my knowledge that the main characters will eventually retake charge of the storyline that keeps me slogging through this less-interesting stuff.
The secondary characters are linked to the main plotline, but only loosely, and I can easily imagine how the plot could be tweaked to make these characters unnecessary. Also, certain revelations in the story were held back longer than they needed to be, in my opinion. The book is about 400 pages, but I'm thinking it could've done its job in about 275.
I love this author's other work and wish this book matched it. Right now, I feel like I'm in an airplane that's circling the airport: just get us to the gate already. And naturally, I'm trying to take this as a lesson for my own work: the difference between building up suspense and dragging things out.