A book does not write itself.
Writing a chapter of a book is not exactly like writing a dozen blog posts. A book chapter requires a sort of continuity of focus that blogging does not require, unless of course you are writing a book for the short-of-attention-span. Maybe that's the sort of book I ought to write.
Writing a book about the joys of riding one's mule is hard to do when one is processing the loss of the joys of riding one's mule due to said mule's being permanently lame.
Writing a book about the children, dogs, cats, husband, rabbits, goats, plants, relatives, neighbors, friends, jobs, hobbies, and delicious meals that make living with a lame mule less sad seems like a marvelous idea.
I haven't given up, but I do think it's going to be a longer process than I thought.