My favorite author and book database is Fantastic Fiction. They do a lot of things right:
1. They cover 30,000+ authors and 350,000+ books, meaning that 99.9%, they have the information for which you are looking.
2. They separate the book information into readable lists: series, including series numbers, publication dates and what format it is, to the new books coming out and their expected publication dates.
3. They include the covers with the books and you can click on the title to get the full book description.
It is my first resource I go to when I am trying to find a list of books in a series. However, it isn't perfect. They do not cover graphic novels or manga. They do not label what audience the book is appropriate for, which would be helpful with authors who suddenly decide to write for a new age group (like YA author Ellen Hopkins and her Triangles book...) They also have lists of new authors and popular books, but there is no way to sort ages.
Check out the screenshot below: