Here's some more info on what constitutes a "series". Generally, a series should meet the following criteria:

Publisher Recognized. This means that the series should in someway be "official". A trilogy or books (or a 4-book or 5-book series) is the prime example. Likewise, a coherent, publisher recognized series of modules (e.g., B1-12).

Smallest Coherent Unit. A series should be the smallest coherent unit that it can be. For example, a series would be "Dragonlance Chronicles" (the original three DL books), not "All the Dragonlance Books" and not "All the War of the Lance books".

If a series is made up almost entirely of distinctive subseries, only create the subseries with this page. For example don't make "The Main Dragonlance Timeline" (which is at a minimum 13 books: Chronicles / Legends / Summer Flame / Dragons of a New Age / War of the Souls) but do make each of the subseries (Chronicles, Legends, New Age, or Souls). Do likewise for the famous T1-4/A1-4/G1-3/D1-3/Q1 series.

Once you have created your smallest coherent units, you can combine them into a megaseries, which should be a subseries of series and/or individual books that didn't fit into any subseries. To access this function, do a "Series Title" search, and then click through to the series you want to modify.

No Replication. A series should not replicate another datum in the index (e.g., "Game System", "Setting"). So, no "Transhuman Space" or "GURPS" or "Glorantha" series. Basically, if you can already get the precise listing via a simple search, it doesn't need to be here.

Single Series (Usually). Usually a book should only be in one series. There are two notable exceptions. First, when the publisher has really marketed a book as part of multiple series.(For example, "Crown of Fire" was sold both as "The Harpers book 9" and "Shandril's Saga Book 2".) Second, when a book is a sub-series that isn't part of a coherent set of sub-series. (For example, B11 and B12 form a 2-part adventure, but are also part of the B1-12 series, and the rest of the B books don't neatly cohere into subseries as was the case for the TAGDQ books. Thus both the B1-12 and B11-12 series should be input.)