I've also recently picked this one up, can you elaborate more on the book? I've been doing drawabox.com and it seems pretty good for muscle memory and skill but otherwise it lacks a lot of areas.
I'm only midway through it, but its hypothesis is that (a) we typically draw using preconceived symbols and (b) we can improve the accuracy of our drawing if we learn to ignore these symbols and focus on what we can literally see (ie., shapes and colours). I don't know how universal this perspective is, but as a beginner, I have found the approach to be helpful.
It's a good book. After following it, I was actually able to draw a recognizable self portrait.
It also reinforced the point that I have zero talent. The drawing that took me hours of painstaking work is something that my wife could sketch in about 30 seconds.
There is an (apocryphal) anecdote about the person next to Picasso at a corrida being amazed seing him sketch a bullfight in seconds, to which Picasso allegedly replied "Seconds? It took me my whole life to be able to draw this."
I'd wager your wife has much more drawing experience than you. If you keep practicing, you'll be able to draw faster and faster.