An article by Joel Friedlander on The Book Designer Site:

As the movement to self-publishing has grown, more authors are producing books that land on the bestseller lists, grab honors in book awards, and receive critical acclaim.

But to do that, publishing industry insiders urge authors to take the time and trouble to make sure their books are “professionally published.”

But what exactly does that mean? How does an author new to book publishing know whether the books they are creating really are professional grade?

To answer this question, I encourage you to take a trip through your own bookshelves, but with an analytical eye.

This makes sense for a few reasons.

most writers are avid readers, with a large collection of books
virtually all of these books were published by traditional publishers employing teams of book professionals
therefore, the best resource for “professional” books is your own bookshelf, where…