From publisher's website:
The Maelstrom RPG, published in 1984 was a small but popular game, released partly on the success of the Fighting Fantasy books, also from Puffin. Despite being in print for only a short time, the game has developed something of a cult following.
In 2007, Arion Games acquired the license to re-release the original book as a pdf. However, the twenty-four years of game design since the original release have produced many new thoughts and theories, and Arion Games wanted to bring the game into the 21st century. Thus the Companion was born.
The 161-page book features a plethora of new livings, an expanded and clarified the combat system, including gunpowder weapons, more magic, including a guide to alchemy, and additional setting information.