Grisham's first thriller, The Firm, didn't really have this problem. It faced up to the law and the Mafia, and played hard and fast without dumping too many of your favourite people. (It also took out a long lease on the American bestseller lists.) The Pelican Brief feels more relaxed (that easy dispensing with possible principals suggests a casual bounty), but the result is a baggy garment rather than something casually cut.
Darby and Gray happen on an eco-conspiracy which goes all the way to the President of the United States; they expose it in the Washington Post and head off to the Virgin Islands to become, presumably, Darby and Joan. At what is possibly the novel's most daring moment, someone mentions Watergate and you remember how a not entirely dissimilar story was both more gripping and more incredible when Woodward and Bernstein told it as fact.
Grisham practised law for nine years, and you can see aspects of that training impressed in his writing - the brisk marshalling of lean facts, the controlled leaking of the evidence, the sprung conclusion. This is why he gets compared with Scott Turow, though the comparison mildly flatters him. With Grisham, the narrative builds up an impressive head of steam, but it is hurrying you past other deficiencies; breezing you through the occasional cluster of samey characters, helping you turn a deaf ear to the undistinguished dialogue, keeping you from wondering where you are. (The main action of The Pelican Brief shifts between Washington, New Orleans and New York, but you would be hard pressed to notice the scene change.)
But one neat structural device separates this thriller from the pack. For the first 200 pages, the reader keeps meeting characters who are completely in the know about the conspiracy; the reader, though, remains in the dark. This tactic works well for as long as Grisham runs it, but obviously it has to be exploded at some point. When that happens, it is with an almighty grinding of gears, an abrupt change of tone and five deathly pages of exposition. Still, it was good while it lasted.