Having a very difficult time with the "camera" book.
I threw out the first draft because it read too much like a technical manual. The second draft is stalled about halfway through. After much analysis, I believe the problem is in the original idea for the book. Jack R. Hart explains the place of the book idea in the writing process in A Writer's Coach. Hart believes that problems with any part of the writing process are invariably caused by a flaw in the preceding step.
My challenge is to come up with a manuscript that is useful, task oriented, and simultaneously interesting to read. If it's not an interesting read, there's no reason to publish.
The best writer I've found in this genre is David Pogue. His reviews and his "Missing" books are models of clarity, humor, usefulness and just plain good writing.