Unfortunately, everyone seems to refer to the Wikipedia article, sometimes simply copying and pasting from it directly, and I've discovered there is a problem there in that the "index librorum prohibitorum" didn't yet exist at the time that Malleus Maleficarum was written. So it may not have been explicitly condemned by Innocent VIII but it is true that he did not commission Kramer and Sprenger to write it, nor did he ever give it his stamp of approval. Whatever really happened in 1490, it is probably pretty safe to assume that Innocent VIII was
not happy when Kramer deceptively used the papal proclamation "Summis Desiderantes" to make it appear as though he had given the book his approval.
Furthermore, though both Kramer and Sprenger were inquisitors, Sprenger was well-respected while Kramer had a reputation (among Catholic theologians and even other inquisitors) of being obnoxious, possibly a little insane, and obsessed with witches. It is possible, likely even, that the whole book was written by Kramer who then decided to give Sprenger the honorary title of co-author so as to further help give the book a semblance of credibility. Sprenger, who died in 1494, was unavailable to object in the 16th century when Malles Maleficarum really came into its own.
Here is one pagan's take on it:
http://www.summerlands.com/crossroads/remembrance/_remembrance/malleus_maleficarum.htm