Why?

As I've mentioned before, I am very pleased with our library system here in Grand Rapids. It really is fabulous. Here's my query for today though: why is it that when I've requested four or five books and am waiting patiently for them to become available, they all arrive within a day or two of each other? In the last several days I've had five books come in for me through the hold system. That will make three trips to the library this week, and three weeks to get five non-fiction books read. Hopefully I'll be able to renew one or two of them -- I'm not likely to get through that many non-fictions in that amount of time.

Though, it is fantastic to get your hands on a book you've been waiting for, isn't it?