Thank you all for your responses - this is really helpful.
I am definitely offering rewards. In fact - this is what I've come up with so far:
Reward #1
Pledge $1 or more:
Thank you for taking the time to contribute - you have earned my eternal gratitude.
Reward #2
Pledge $5 or more:
In addition to my eternal gratitude, you're also getting a copy of the E-Book!
Reward #3
Pledge $15 or more:
In addition to my eternal gratitude and copy of the E-Book, you are also getting the Paperback, shipped right to your door!
Reward #4
Pledge $25 or more:
You guessed it, you're getting my eternal gratitude, copy of the E-Book, and a copy of the Paperback straight to your doorstep, but you're super special, and your paperback is going to be signed by me, with whatever* inscription you want (some restrictions apply - I will not sign away all future profits or my unborn children).
Reward #5
Pledge $50 or more:
You're getting all of the above: my eternal gratitude, a copy of the E-Book, a signed copy of the Paperback, AND I'm going to mention you in the acknowledgements as the wonderful person you are.
Reward #6
Pledge $100 or more:
Wow - you are truly amazing. You are going to get my eternal gratitude, a copy of the E-Book, a signed copy of the Paperback, a mention in the acknowledgements, AND a PDF of the manuscript before it is released.
Reward #7
Pledge $150 or more:
Did I say amazing? I meant AAA-Mazing. I mean, really, you are a saint. And you know what sainthood gets you? My eternal gratitude, a copy of the E-Book, a signed copy of the Paperback, a mention in the acknowledgements, a PDF of the manuscript before it is released, AND a PDF of the cover image before it is released.
Reward #8
Pledge $200 or more:
Pulling out the big guns, huh? Sainthood wasn't enough? Well, don't you worry, I've got something really special for you. In addition to my eternal gratitude, a copy of the E-Book, a signed copy of the Paperback, a mention in the acknowledgements, a PDF of the book before it is released, a PDF of the cover before it is released, I am going to DEDICATE my book (my first!) to you.
Reward #9
Pledge $500 or more:
Limited reward (4 of 4 remaining)
I've saved the best for last - just for you. You amazing, wonderful, beautiful, fabulous, most-awesome person in the world. You are going to get all of the above: the gratitude, the E-Book and signed Paperback, the acknowledgements, the PDFs of the book and cover, and the dedication, plus the coolest thing ever. I'm going to re-name one of the characters in the book after you, thus immortalizing you forever in print. That's how much you mean to me.