Thanks for all the libray/book procurement suggestions!
I have used Ebay in the past for out of print books I wanted (like the older version of How Things Work and an old Jr Britannica) but I never thought to buy in bulk there. I bid on some stuff yesterday.
Our library system does allow you to search and reserve online. You can have the books delivered to the branch of your choice. But what happens is that the order comes in piecemeal and they only hold them for a few days. Also, there have been several instances where a book that is listed as available and waiting for me is nowhere to be found. In the past I have used the function to try and get several books in a range of difficulty on a particular theme. And if I end up with only half sometimes they are all too hard, or all too easy, or I get the first and fourth book in a series......
So maybe the solution is to go with quantity, not a targeted theme. Just order a whole boatload of decent books and let the boys read them hit or miss. It's obviously a good tool, maybe I have just been trying to use it with too much precision.
The idea of trying to cultivate a relationship with a librarian is also a good one. ALthough I've found the system a little lacking in practice, all of the librarians I have spoken with have been very kind and helpful.
I probably sound very impatient and lazy, but I work full-time so that makes it a little harder to stay on top of this stuff.