I was *determined* not to by HPatHBP. Determined. I walked past bookstores offering it for preorder ridiculously cheaply countless times. I was absolutely determined that I wasn't going to waste my money on a copy just yet - wait a few months till the paperback comes out, I told myself. You'll save $10-$15, the writing will be just as good then, you won't lose anything..
My determination lasted until my train went through Central. The solitary person in my carriage reading the book, that I could withstand.
The fact that 40% of the people waiting on the platform at Central were carrying a copy - and a further 30% were *reading* their copy - that I couldn't withstand.
I know own a copy of or HPatHBP. I've read two chapters already.