Project Notes: I found this tutorial on SewMamaSew. It was love at first sight! I started with a muslin, with which I had much trouble! I also had some troubles getting the fit right on the final piece, but in the end it worked out just fine, and I’m very happy with the final product! The tutorial can also be found on the designer’s personal blog, made by rae, which I discovered through this tute, and think is great! 
I shortened the straps and didn’t do the optional curving of the side seams.
Mistakes/Complications: This is one of those patterns that you draft yourself based on your measurements. Making the muslin, I got into the type of trouble that is typical for me - despite having pattern pieces cut out to specific measurements, I cut a slightly different width on the bottom part, because I wanted to use a scrap that wasn’t quite wide enough. Not smart, since I’m not lacking in any muslin! I had to fiddle with corresponding pieces SAs and do a lot of tearing out and re-sewing as a consequence. I also had a little trouble understanding the directions for creating the pleats.
I know that when I made the final top, I had some trouble too. But sadly, I don’t remember exactly what it was. I think it was just that when I went to attach the straps, the back billowed out to much and fit poorly. I did a lot of raising and lowering where it attached in the front, and the back, and in the end, I attached the back pieces at an angle as well, and that did the trick. I have narrow and sloping shoulders, so this sort of thing was bound to be a problem for me. The funny thing is, there really is a front and back now! If I put it on backwards, the straps keep falling down and it feels less comfy!
Notes for Next Time: I will shorten the straps even more, because I ended up trimming quite a bit. Also will try moving the straps in maybe a half inch each, to see if it fits better. I think it would be interesting to try pleating the fabric first, then cutting and making the top band, and measuring its final width (adding in the SA) and using that number to cut out the pleated bottoms.
Actually it might be interesting (and easier :P) to leave the front pleated as it is, but for the back just do one wide inverted box pleat, sewn down fairly low so that it lies fitted for ~ the first third of my back.
Tags:
top 
But it is an absolutely lovely idea. Click on the far right thumbnail to see the finished product - the main photo on this page actually just shows a kid in front of a regular bookshelf - which is what you are making an alternative for!