My process probably isn't much different and thinking through it helped me realize what the issue is with the series I'm debating over. (Exactly the point :) )
The series is Jacqueline Carey's "Kushiel" series. I really liked the first book. The characters are what did it for me. They were funny, interesting, sneaky and complex. She killed two of them - effective for the plot, but by the third book I realized that what I liked about the first one was the two characters that were offed (I'm not spoiling a plot line here, I promise.)
The books are mammoth, weighing in at 700 pages each in hardcover. They are written in trilogies. If I decide to read book four, I'm really committing myself to three more books.
Here's the problem: While I liked them, I didn't love them, but I don't have any alternative series to read instead. I'm caught up with most of the series I'm reading or am waiting for the title to come in at the local library.
Since time is tight, I don't have the luxury of browsing shelves. I stick with series that while I enjoy them, I don't love them.
I still don't know if I'm going to get book four. After all, the latest installment of Jim Butcher's Dresdyn Files just came in. I'm dying to know what's going on in Chicago. But after that one, I'm waiting for either the author or the publisher and I'll have to decide what to do with the Kushiel Series.
Unless someone has some suggestions about a series that they are in love with.
Cross posted at Starting Write Now