I just finished TheMagic Words: Writing Great Books for Children and Young Adults by Cheryl B. Klein and I completely understand why this woman is such a respected editor. If you are writing children's literature, you will want to read this book!
Some topics covered:
Creating multidimensional characters
Building a bond between the reader and the characters
Writing outside your own perspective
Writing Good First Chapters
The book is thorough, logical, and very straightforward with examples and tons of exercises on each element of a great book. There are checklists within the chapters that really help authors examine their work more deeply to flesh out weaknesses and strengthen these individual elements during revisions. Other than taking a course from, or actually getting your manuscript acquired by an editor at a major publisher, I can't imagine what else has the potential to really improve your writing.
Now that I've raced through reading it, I'm going to use it as a master class for revising my WIP.