"He reads too fast for me."
Translation:Er liest zu schnell für mich.
Well, the sentence in this exercise does not specify that he is reading "to me." He could be reading to a group of children, and "I" think he is reading too fast as I listen.
The original sentence's "me" is not the indirect object; it would be if it said "He reads me the newspaper." I think your new sentence would be correct, if you wanted it to be translated as "He reads too fast to me."