This must have been what was on my mind when I was hesitant about writing a memoir about depression and being on Prozac when I was inspired to write about this after reading the best-known account of the iconic medication. I felt I was stealing the author's thunder. But I was soon convinced that everyone has a different story to tell. That more than one survivor of the Titanic, for instance, should be allowed to tell their story, not just one such person. As it says above use your unique perspective to make your book different, something I was told in the beginning I gradually realized that I wouldn't be copying others, that I was just being inspired by them. Depression is a universal problem and everyone has a story to tell, even if some of what they went through was similar, if not identical to, that which others faced.
I have been working on the diary novel, but I'm not sure what really inspired me in that instance. I've read The Dork Diaries series, but have yet to read the Diary of the Wimpy Kid books. But my main character is starting to sound like ones in these books. I sent one of my mom's friends an email attachment of my story and she described the main character as being extremely cynical and unsympathetic, and "always seeing the worst in every situation." But that's just one person's take. My mom doesn't agree from what she'd read so far. I now need others to read this one to see what they think.
Nearly every story has been told more that once, but your voice is what makes it stand out. This was a lesson I learned when I began deciding if I wanted to begin the memoir.