I'm not really sure if there was a book release party for every book, but I'm fairly certain nothing was available to the public for the first book! The fans weren't around, yet. I posted an inquiry
at the COS Forums. It'll be interesting to read what people have to say.
All I know, is that I first became aware of book release parties when book six arrived. My sister and I attended a book release party, at our local mall for Harry Potter and the Half Blood Prince. So much happened that night, and we did so much in preparation! We made Harry Potter treats, we taught a Dueling Game, we brought prizes, our sister-in-law -Mandie- made costumes for us .... what else.... oh! My sister and I were the first to arrive (we were there about 8 hours early), and we received the first tickets! My sister let me have ticket number one, because it was my birthday. Yay for Sissa! Umm ummm, what else.... my boyfriend came too -that made it even more special! His birthday is right before mine --I bought him a Slytherin teeshirt. Oh! My sister and I both won prizes for our costumes. Our pictures were in the newspaper. That was pretty spiffy.
Ha! All these memories are rushing back at me now. I remember as we were waiting for the event to start, a lady came by, and started to preach at a group of us about the "real and better power of God". We had a fun chat with her --and I've gotta say, it was amusing to hear my sister tell her that she was a Christian herself, and didn't need a lesson on Christianity.
Oh yeah! Hehe! When we bought our books, TONS of people were in line behind us. I dared to open up my book, and say stuff like "Oh my god, Harry Potter dies!" I got a few dirty looks --- oh, it was great fun.
Sarah (left) and myself (right)
A view of our table
Anna looking at the treats we made!
Our Cauldron Cakes!
Our Pumpkin Pasties!
Our Trelawney Tarts!
Ian receiving his birthday present!
Ian, Kate, Sarah and I
This is a short video clip of my sister and I, dueling.
That night, my sister, my boyfriend and I hung out upstairs, reading the book. They're both faster readers than I am, and they kept on talking to each other about what happened --without letting me know what had happened --but I could tell it was really BIG. Ergh! It was driving me crazy, and I know they enjoyed that! They finished the book before I did, and I finished it a day later. (I read a LOT -and I'm not a slow reader; I'm just not a particularly fast reader --I have to periodically stop and think about what I just read, instead of rushing through it.)
Oh, something funny --and kind of sad --- My father hadn't finished the book yet, and one day, I was in one room, and my father was in another; and just had to burst out "I can't believe Dumbledore is dead!!!" Then, from the other room, I hear "Gee, thanks!" Ha! My poor Dad! I didn't mean to spoil it for him!
Though, looking back, I'm glad I saw it alone -I didn't have any distractions, which made it possible to become completely immersed in the story of Harry Potter. 
Wizard Rock -What is it?
I've had the opportunity to see Harry and the Potters twice! The first time, it was at a university bookstore. The second time, it was at a mall -though, the concert was sponsored by a library. 
