Very generic. Lacked some details that I thought was noteworthy in some villains. However, considering the volume I guess there was only so much that could be entered. All up not too bad a book for a general reference guide. Especially good for the old villains well out of print and general knowledge.
Another comprehensive tome, also provides color illustrations, and criteria for what makes a super-villain stand out from ordinary villains. Villains are not limited to comic books although that is where they are most extensive; all forms of media have villains to offer. A truly excellent encyclopedia.