A cleat is a good idea -way easier than mortise-and-tenon- and shouldn’t be too obtrusive either. Might have to use individual cleats, though, since the rails are at different angles.
Here are a couple more pics I found.[attachment=2]rack.jpg[/attachment]You can see the angle of the front rail here.
These next two are both listed as deluxe models, but they’re designed differently.
This one has an extra back board and a beefed up front rail (a T system, it seems)[attachment=1]rack2.jpg[/attachment]
This one also has the extra back board, but just a single front rail (and it’s not edgewise, either).[attachment=0]rack3.jpg[/attachment]
Looks like all the models use veneered pressed board for the book ends. I have enough red oak left over from another project to make the rails, back boards and dowels. I bet if I picked up a half sheet of red oak plywood I could make both book ends out of it (the manufacturer lists the dimensions as 37-1/4" x 23-14"). Then I’d just have to figure out how to finish the plywood edges.