A series is defined as two or more books that share the same characters, setting, and/or locale, and the story arc develops in each subequent book in the series.
If you like to read books in series, you will love the eSequels database! Click on the eSequels link from the library's "research" page. You will need to enter the 14-digit barcode from your library card when prompted. Based on the print title Sequels, eSequels is the always-being-updated online version and has listings for adult titles, from Christian fiction to gritty noir mystery series. You can search eSequels by author, title or character, or by location, subject or keyword. Each entry will give you information about the author and the series, a link to the author's homepage and and annoated listing for the titles, in series order. (Don't worry, the annotations will not "give away" any crucial plot points).