d20 Modern's quick take on martial arts left many wanting more, and RPG Objects is there with this excellent supplement. Anyone who has been a fan of the Blood and * series as long as I have won't be surprised, or disappointed, at its high quality.
Blood & Fists opens with several martial-arts related advanced classes like the burly Barroom Brawler. They would fit right into most action-oriented d20 Modern games. Of particular note is the Martial Arts Master, whose special "masteries" are similar to talents, but focused entirely on martial arts. They get their own section near the end of the book.
The way that martial arts are integrated into d20 Modern is through the feat system. By selecting a martial arts style feat, moves and even some new skills are unlocked for a character. These style feats are therefore more powerful than many d20 Modern feats - and the game explains this, a welcome addition to those who are concerned with game balance when looking at third party supplements.
The styles themselves are presented each in a paragraph, each categorized and the categories explained, so that GMs who wish to create their own fictionalized style can make them similar to existing styles. Advanced uses of martial arts styles are called maneuvers or signature maneuvers and cost an additional feat.
Finally, "ki feats" introduce a new form of FX to D20 Modern, similar to what one might see in a modern martial arts film or TV show.
Perhaps the strongest section of the supplement is the description of several martial arts-focused campaigns, from wandering students searching for a legendary master to a rival-school fighting tournament setup, which is fleshed out in its own chapter.
These kinds of examples are key when you're trying to decide if you want a third-party supplement to a highly detailed game. It tells you how you can incorporate the material into your own game and what kinds of games you can expect to have.
The ZIP file comes with a print version, a screen version with landscape orientation (!) and a character sheet, all of which are welcome additions that garner this supplement my highest marks. I even sought it out in print because it was so useful to me in my d20 Modern games. If you want to incorporate martial arts material without completely replacing the system (as other games like Spycraft do), this is an outstanding choice.