It depends on the book. I like fantasy novels with longer or more whimsical names (like George R. R. Martin, or Cinda Williams Chima), maybe even some mysteries the same way. But generally it depends more on the name than the writing. Say you're writing a detective novel and your name is Jessica Annabelle Jones. J. A. Jones is a little more intriguing than Jessica Jones on a mystery. But on a chick-lit novel, J. A. Jones just looks pretentious.
Sometimes you have a particular reason. For J. K. Rowling it was because the ambiguous initials didn't reveal whether she was male or female, and according to her publisher, books by men sell better. Other female writers, like E. L. Konigsburg, have done the same thing.
I don't care. Is your book any good?
I agree that I care more about the book, but I understand wanting a pen name to look nice.
I think it depends on the name.
If your name is Laura Smith then changing it up with initials or middle names or maiden names can be very helpful in making your name memorable. Because L.R. Bantam-Smith or Laura Berlin-Smith could definitely improve it.
If your name is already something like Verity Chadwick-Burns then you probably shouldn't worry about trying to mix it up.
Though, honestly one of my biggest pet-peeves is when books have the name of the author larger than the name of the book. I honestly don't care who the author is, so filling the whole cover with their name and having to search around for the actual TITLE is ridiculous!
So given the option, I'd prefer a shorter name to a longer one. So in that sense Harper Lee and J.K. Rowling are my favorites! And funnily enough those are my favorite writers on the list as well (Fitzgerald is great, but his plots are dull as dirt)