From publisher blurb:
New tables expanding usage of the infamous item!
Reprinting and expanding on the table in the Dungeon Master's Guide, this product quadruples the possible outcomes of using a wand of wonder with three new tables: a table of Uncommon results, a Rare table, and a Very Rare table. Experience the joy and/or horror that comes from a roll of chance with the wand of wonder. The memorable chaos that uccurs when a player uses this wondrous wand and the best imaginable outcome or the worst possible result. Or just summons a herd of cows.
Whether you're using the regular wand or it's hardier cousin the rod of wonder this book adds a little fun/chaos to your game.
Remember, when in doubt: say "Wubba Wubba!"
Edit: Printer Friendly version added.