80-Page Giant

80-Page Giant was the name used for a series of comic books published by DC Comics beginning in 1964. The series was named for its unusually high page count. (The typical page count for American monthly comics at this time was 32 pages). The cover price was initially 25 cents, while other comics of the day were rarely above 12 cents. Many of these "Giant" issues contained reprinted material, often including material from the Golden Age era of comics. Each issue would focus upon a particular DC character or group, such as Superman, Batman, or Jimmy Olsen. The 80-Page Giant format and numbering would later be used for special extra-large, reprint-heavy issues of their regularly published titles.
In the late 1990s, DC Comics began publishing 80-Page Giant specials which were special publications relating to a series (including "Secret Origins", which had not been an ongoing title for years) and which were usually compilations. 
Around this time, DC was also publishing reprint-themed 80-Page Giant Annuals (also called "100 Page Spectaculars"), some of which were reprinted replicas of past Annuals and some of which were newly published reprint collections styled as the Annuals of a Silver Age title that had no Annuals during its actual run.
Number of pages.
Originally, the Giant issues were all labeled "80 Page Giant". When the number of pages was decreased (usually to 64 pages), the "80 Page" part of the title was dropped and the title changed to simply "Giant" or "DC Giant".
Types of Giant comics.
There were four types of "Giant" comics:
Issues G1 to G15.
These issues were published under the "80 Page Giant" title. They had "80 Page Giant G##" on the cover.
Issues G16 and up.
These were published under other series titles such as "Justice League of America #39". In other words, "80 Page Giant #16" is the same as "JLA 39". These had "80 Page Giant G##" or "DC Giant G##" or "Giant ##" on the cover (for example, "80 Page Giant G16").
The following is a complete list of the issues, ordered by date:
Annuals.
The following "Giant" issues were the forerunners of the 80 Page Giants ("80 Page Giant G01" was originally advertised in DC titles as "Superman Annual 09").
The new 80-Page Giant (1998–2003).
DC published a number of 80 Page Giant specials within various current series. These began numbering with #1 within each series.
The following is a partial list of issues, sorted by title: