The Pathfinder Adventure Path is a monthly 96-page, perfect-bound, full-color softcover book. The line was created by the Paizo company to replace Dungeon and Dragon magazines when they lost the rights to publish these.
The concept is based on the Adventure Path series of linked adventures that Paizo had been running for several years in Dungeon magazine. Each volume which are numbered sequential on the spine like a magazine but not dated, contains an in-depth Adventure Path scenario, stats for about a half-dozen new monsters, and several support articles meant to give Game Masters additional material to expand their campaign. It is like a magazine in that it is published monthly in number volumes and can be purchased by a subscription, however does not contain current news type information typically found in magazines and volumes are not dated. Each adventure path arc runs over 6 volumes.
The first 4 arcs (24 volumes) are designed for base OGL system 3.5 compatible, from volume 25 onward they are designed specifically for the Pathfinder Roleplaying Game (1st Edition). The arcs so far (as of November 2015) published or announced are: