Johanna Rothman gives a very interesting take on how to convince your manager to buy books. If you don't know who she is, she's a world class consultant who's also been doing lectures here in Israel at SELA university about product development and project management. We've also met her for a Blogger dinner some time ago, it was really interesting.
I don't think there is one developer I know that thinks books are not a good investment. That many smart people can't be wrong.
BTW : one comment listed under Johanna's post says that the guy would rather buy his own books so that he can take them with him when he moves jobs. Definitely something to think about. One thing you need to remember is that regardless of management - you should worry for your own education. No one else will. It also makes for a great answer to one of my favorite interview questions: “So tell me about the last book you've read to do with technology”.