Someone in your dept has to have a copy of it. Ask if you can borrow to "brush up."

Borrow the book from the library.

Ask your employer to buy the book for the office, others can read it when you are done with it.

Did you exaggerate you knowledge about this subject? If so, I wouldn't ask them to pay. If not, I'd have no problem asking them to pay.

I think it depends where you work. I work for the federal government and haven't had one training that cost money in over 3 years. No way would they buy me a book. We're hard pressed to get paper for our printers.

It's professional development. As a supervisor, I wouldn't blink an eye at the request.

At $50 I doubt the company would put up much of an argument against buying it for you. Can others in the office use it as a resource? But if you could always buy it and ask if you can be reimbursed.

I need a book on a subject that is relevant to my work (a technical book) and it costs about $50. Nobody told me I need to read it, but it's on a new tool we have been using that I feel I need to gain deeper knowledge of. Should I just buy the book myself, or can I ask my employer to purchase it for me? I feel weird asking b/c it's an admission that I don't know as much about this as maybe they think I should. But I also don't want to spend $50 on a book I wouldn't purchase for my own enjoyment.