Treasure Hunter is a d20 Modern campaign kit for pulpy adventures in the style of Indiana Jones or Tomb Raider. It is notable for adding quite a bit in the rules department towards the genre, like using the Reputation score to allow access to restricted areas. Chase rules are included as well. Quite a bit of fluff, in the form of cool settings and advice, appears too. Its standard of fidelity to a "real-world" setting where magic is subtle and often off-screen (again, think Indy) is admirable.
Additionally, many feats and spells from other variations of d20 rules are included (especially nice is the section of typical traps for many levels). However, some of these additions are not checked for their suitability to a "real-world" setting (for example, several of the traps use purple worm poison instead of selecting a toxin from the main book or web enhancement).
Still, the good far outweighs the bad; especially at the price.