Both are great - and as Lex points out very different. I would consider both to be "must haves".
The current Whisky Bible 2005 - with over 2,750 whiskies tasted, evaluated and rated - is all but sold out. Jim is hard at work on the the 2006 (3rd edition) - with even more tasting notes to be added (with the hope of a greatly enhanced Canadian Whisky section)... It is due out in the fall. It is a portable reference and a great tool. Jim notes new additions each year with a symbol - summarizes his scores and balances his point system by assigning scoring for - Nose - Taste - Finish - and Balance - each out of 25 to accumulate to a score out of 100.
There were two books published in 1997 with overlapping text - the book you mentioned:
The Complete Guide to Whiskey
: A Guide to the World's Best Scotch Malts, Irish Whiskeys, & Bourbons (softcover - and a similar size to the Whisky Bible)
Jim Murray's Complete Book of Whisky
: The definitive guide to the whiskies of the world - in Hardcover (a coffee table sized book with the addition of great photography). This was one of my first whisky books and a favourite...
As you noted, Jim has a talent for writing, a gifted nose & palate and a passion for Whiskies of the World.
I own all three books and endorse them highly.
P.S. - in the interest of full disclosure: The West Coast Whisky Society is assisting in arranging for Jim to do a Western Canada tour (Tasting Events in Victoria - with the Victoria Single Malt Club and The Strath - Wine & Spirits, Calgary - with Willow Park Wine & Spirits & Vancouver) in May. While I have not personally met Jim yet - I was such a fan from the first book I contacted him last fall to order the Whisky Bible 2005... and have since been involved in organizing this tour. So - you can call me biased or you can call me a fan... I just consider myself a whisky nut...