ESSENTIALS OF SCREENWRITING by Richard Walter is also an essential book for writers of all sorts.  He gives some of the most concrete advice on the nuts and bolts of good storytelling, some personal anecdotes from his tenure as a UCLA professor, and excellent query advice.
Yes, of the two projects that are currently underway...one is a screenplay, the other is another novel.  I would rather work on one at a time because that just seems like a better plan, but neither story will go patiently sit on the back burner.

http://www.undergroundbookreviews.com/3/post/2013/06/review-of-room-four-by-a-j-knauss.html
Interview will be on line tomorrow.  Writers: constructive criticism is worth its weight in gold.  Friends may cheer you on and tell you "it's great" but the best help comes from those who point out the flaws.  Every book should teach you how to write the next book.  Or the next screenplay.
Underground Book Reviews does a weekly e-newsletter that is an enjoyable read.