Dune Trader is a background expansion for the original Dark Sun campaign setting. It is a glorious delve in to the trading houses of Athas, both the city-based, right to the Elven tribes that wander the desert. In that regard, it is mostly as good as Slave Tribes is.
For each of the major trading houses (which is roughly one per city-state), the book gives a solid overview of their assets, current socio-political situation and outlook, rivalries, and what the ordinary person on the streets might know about them. This makes this source book a good one: lots of fresh information about a vital part of the economy.
The minor houses and the elven tribes makes for interesting reading, and is part of the book that could be transplanted to other realms and settings with modest ease. For example, House Ianto (a minor house) is portrayed as a house that has fallen on hard times due to the slaves revolting in Tyr and the iron ore no longer flowing. They're trying to rebuild their trade based on silks and own a fort to the South of Tyr to help them do so.
Other positives about the book include the introduction of the trader class (now not really too relevant in the current dungeons and dragons iterations - but good for the time of publication and for 2nd edition) and the trader campaign in general: i.e. the PCs as Dune Traders and how they might get crodlu and kank beasts pulling their wares across the desert and what sorts of adventures might be possible (especially if they're playing on behalf of one of the big houses).
On the negative side, I really didn't like the fact that they presented mechanics for bartering. Seriously: this can be totally role-played. Why are we rolling die for this? (well, okay, I guess there might be reasons for this, but I think more fun could be had with a direct negotiation for a critical deal. And in Athas, all deals will probably be critical to the success of a trading House). The Elven tribes won't be that transplantable to other settings due to their uniqueness (and there's only 2 of them described), but I suppose that substituting a different race wouldn't hurt in any transcription to a different plane. Overall, the book is nice and provides plenty of hooks for the small-scale trading adventurer(s), but I didn't really care for the mechanics or the detailed statistics of some of the characters. That's not to say the rules are bad - simply that I wouldn't automatically use them. So 4 out of 5 stars from me for this expansion book.