https://www.comixology.com/Robin-101...Robin_101_Sale

They've got Robin's (Dick) first appearance in Detective 38, Robin: Year One, and many other books about different Robins, on sale. (though, the book counts definitely favor Damian)

Count breakdown:

Dick Grayson: 20 books
Jason Todd: 6 books
Tim Drake: 11 books
Stephanie Brown: 2 books
Damian Wayne: 62 books