Pilot Workshops has published updated versions of its Pilot-Friendly manuals for the Garmin GTN 750 and GTN 650 touch-screen navigators. More details and samples here.
Full disclosure: I was the primary author of the new GTN editions, with a lot of help from the editors and graphics staff at Pilot Workshops. I also contribute to the company’s IFR and VFR training scenarios.
The books are available both in spiral-bound print editions and as PDFs.