Batman: The Man-Bats Attack was small book published in 1991. It was the third book from a series of four to be published by Ladybird books.
This was the introduction inside the book:
"Gotham has a new line in Crooks. The Man-Bats are out in force, ready to terrorise the city and raid banks. Even Batman may not be able to defeat them..."
Vengeful scientist Dr. Darrix hacks into the computer files of Dr. Kirk Langstrom, the original Man-Bat and uses his serum to transform criminals in dangerous Mutant Bats that terrorise Gotham City. Batman has to do everything he can to stop them...