The pictures of your work help on a diagnosis. There are many ways to achieve the look you're going for and it appears to me you're using a standard beveler. A figure beveler is a far better tool for this type of work, but a modeling spoon will work in place of one of you don't have any. As for the book, Al tells you what tools he uses for every image in it. If you don't have those particular tools, you'll have to improvise. What the book can't show you is the technique. Only the aftermath.
The reason you don't like the depth isn't only because of the matting, although that will help. What's causing you problems is the steep little Vs where you beveled, with the surrounding leather still at the same level like a plain of wood with channels routered in it. You have flat leather with those Vs beveled in it. What you want to do is create wide stair step effect, with each peak or valley standing at different levels (Or at least appearing to do so).
Lastly, your book has everything you need to know, but if thats still not enough, seeing HOW the technique is done can help tremendously.