Looking to find out what the order of books in a series? All series by a particular author? Whether a book is part of a series? Look no farther – the websites below have the information you want!

What’s Next
Created by the Kent District Library of Michigan, What’s Next contains listings for thousands and thousands of both adult and children’s books. It is extremely easy to use, and you can search by author, title or series, and limit your results to a particular genre (e.g., romance or science fiction).
FictionDB provides both free and fee-based services. Free ones include browsing list of series by author or by publisher, links to book reviews, information on upcoming releases and more.
Fantastic Fiction
This site, from the United Kingdom, contains bibliographies for over 20,000 authors and listings of over 270,000 books.
Juvenile Series and Sequels
The ‘Juvenile Series and Sequels’ database, created and maintained by the Mid-Continent Public Library of Independence, Missouri, currently contains over 25,000 books in series titles that are classified into three audiences: Young Adult (6th through 12th grade); Juvenile (2nd through 6th grade); and Juvenile Easy (birth through 2nd grade). You can search by author, book title, series title or subject.