Published by Wizards of the Coast.
The first offering published by TSR UK, The Sinister Secret of Saltmarsh set the standard for the installments that would follow it in the U and UK series. An introductory mystery-style module, the adventure writes the first chapter of a plotline that continues in U2 Danger at Dunwater and U3 The Final Enemy. Not surprisingly, the writing here is top-notch, the plot twists clever, and the atmosphere engrossing–traits that (IMHO) infuse all the modules this fantastic team presented. U1 is certainly suitable for experienced gamers beginning a fresh campaign, but it really shines in its potential for new DMs and Players.
Read the Full Review at Dragonsfoot
What really stands out about U1 are two things. First, it takes the standard low-level D&D tropes — an isolated town beset by problems appropriate for 1st-level characters to deal with — and gives them a new spin. The town of Saltmarsh itself is given glorious life through its many NPCs, including criminals in league with smugglers who are using a nearby abandoned reputedly haunted mansion as their base of operations. What’s terrific is that the mansion is not in fact haunted at all but is only made to appear so through the use of illusion magic and other trickery. The vast majority of the enemies the PCs face initially are in fact human, which puts the module very much in line with the traditions of pulp fantasy.
Read the Full Retrospective/Review at Grognardia.