Star Trek Sketchbook, by Herb & Yvonne Solow, is light on text, but full of pictures showing work by Matt Jefferies, Bill Theiss, Fred Phillips, and Wah Chang, including some I'd never seen before. It's a large format paperback with a fancy arrowhead cutout in the cover, so used copies might be torn.
I found mine bundled with John Eaves & J.M. Dillard's ST:TNG Sketchbook - The Movies (Generations and First Contact), which is filled with Eaves' design concepts.