Qadira, Gateway to the East is a 36-page source book about what could be called the "Arabian Nights" area of Golarion. Retroactively listed as part of the Pathfinder "Player's Companion" line of books, this is probably as much or more for the GM rather than players. It's an impressive and well-written overview of the land, and there's definitely a lot of bang for the buck here. The book includes a full-color map of Qadira (sparsely annotated, to be fair) on the inside front-cover and is then separated into seven sections:
* A ten-page introduction to Qadira. This section discusses the history of the area, its political situation in terms of leadership and relationship to nearby lands, what goods are traded, and how the people are divided into four groups: nobles, citizens, slaves, and foreigners. It also includes descriptions of major cities and landmarks in Qadira. A sidebar introduces one new feat, one new combat trait, and two new regional traits.
* A four-page section labelled "Society." This is a quite useful overview of how the core races and classes are perceived in Qadira, and has a useful (if brief) discussion of cultural quirks. This section would be quite useful for players interested in creating a Qadiran PC. A new social trait appears here.
* A four-page overview of Katheer, an important city in Qadira. This section includes a half-page map, discussion of some major areas of the city, and four individual NPCs (description only, no stat blocks) that could come into contact with adventurers. Two new regional traits and an item are introduced here. This section is mostly for the GM.
* A two-page section titled "Combat" that consists solely of a prestige class called a Daivrat (a spellcaster who befriends genies). I've never played or seen one of these in a session, but the mechanical abilities don't seem to really do enough to draw out the flavour of the concept.
* Two pages titled "Faith." This section includes very brief discussions of the role of Irori, Sarenrae, Rovagug, Abadar, and Gorum in Qadira before introducing a pretty powerful new item ("War Kilt of Sarenrae") and a new feat ("Dervish Dance").
* "Magic," a short section that mentions some different traditions of magic in Qadira (like Veil Magic, Warding Magic, and Gen Magic) but unhelpfully doesn't cover in any detail whether these traditions have any real differences compared to the common schools of magic. Five new regional traits and the alchemical substance silversheen are introduced here.
* A six-page bestiary with stat-blocks for the half-janni, suli, and zhyen.
As best I can tell, much of this book was written before Paizo had clearly differentiated between its Player's Companion line and its Campaign Setting line. Qadira, Gateway to the East has much more in it of interest to GMs (a bestiary, an overview of a major city, etc.) than it does to players, while still introducing enough traits, feats, and even a prestige class to hold some value to players. It's a bit of a confusing mix, but, as I mentioned, it's a well-written product overall. More recent comers to Pathfinder might be warned that the artwork, although fine, is not up to the later Paizo standard.
As this review is being written, a new book about Qadira is on the horizon, titled (rather too similarly) "Qadira, Jewel of the East."