Books came tumbling down!

I think the cakes were just too heavy and too small to be stacked. The top cake slid off less than a block away from its destination. I made a new "book" to replace the bottom one but less than an hour later after replacing it, the top one slipped and crushed the bottom one again. The dowel didnt help any. It was ok since it was for my husbands employee. They just cut the cake up in the kitchen and took the pieces out to the party area. Next time we will engineer it better LoL