As someone who is evolving into elearning design from a technical writing background, I found Cammy Bean's "The accidental Instructional Designer" (The Accidental Instructional Designer: Learning Design for the Digital Age) to be very encouraging. It's great to know that there are many others out there who are succeeding in this field without having come from a formal instructional design background. It's also good to find out that not having the formal background isn't as big a handicap as some might lead you to believe.
This book is full of information from someone who arrived in the field from an indirect origin. Cammy covers some of the classic things not to do and provides solid advice and resources on doing it better. For anyone who finds themselves in the position of having to create online or digital learning, I would highly recommend reading this book from cover to cover.