Campbell Black novelized it, which is its own strange process that is sometimes hard to pull off to the authors' and the readers' satisfactions. Black did it well. It's based on a slightly earlier draft of the Raiders script, and stuff gets changed during film productions all the time, so novelizations never quite match the final film -- the fate of Toht (the creepy little Nazi who burns his hand on the medallion) is different, for instance. Generally, the film improves on what was in the script Black used: Indy and Belloq's final direct confrontation is a little too passive in the book. (The film's version of that scene, where Belloq calls Indy's bluff, is a stronger moment than what was first scripted.) But it explains things that the film doesn't quite explain, like why Indy knows not to look at the Ark at the climax.
The book even has poetic flourishes. Part of me kind of wishes Black had gone in a more pulp-fiction direction, but he wrote the novelization with flair. And that's welcome after the lame Empire Strikes Back novelization I read back in January.