The simplest looking projects often involve a lot more work than you think, and this was certainly the case with this cube shaped rack.
The initial problem was deciding how to joint the long pieces to form the criss cross in such a way that they all lined up perfectly and remained strong. I did contemplate using just two long pieces and then fixing on the other pieces dowels or biscuits, but this was soon dismissed for several reasons. For a start I thought it would be difficult to get them all perfectly aligned, any slight discrepancy would be immediately obvious. Secondly, the joints would be quite weak and probably wouldn't withstand the leverage if the shelves were to be loaded up with books.
In the end I settled on using 4 long pieces and cross halving them to maintain maximum strength, and there then is no way the resulting boxes can end up out of line. The next problem was deciding on a joint for the short end pieces. They could just be butted on but I felt this would look too chunky. Another alternative was to dovetail them using a router jig, but the material was a little too thick for this and I there was certainly not enough budget to do it by hand! In the end I settled on a straightforward mitre joint but strengthened with a biscuit using the jig described elsewhere in this issue.