eBook Cover Design for a Software Dev. Book

I'm a freelance software developer, primarily working with Ruby on Rails. This year I'm making the conference circuit, giving deeply technical talks on the Ruby language. This project is for an eBook which grew out of one of those talks.

Ruby language software developers. The sort of people who read my developer blog (http://avdi.org/devblog), read Ruby Inside (http://www.rubyinside.com/), and buy PeepCode products (http://peepcode.com/).

I need a cover for a short (40-50 page) eBook. The title of the eBook is "Exceptional Ruby". It is aimed at intermediate to advanced Ruby developers, and covers various topics related to handling failures and exceptions in Ruby code.

* It must be sized to fit well on an 8 1/2" by 11" page in portrait layout.
* It should suggest "Ruby" and the concept of failures or errors in some way.
* Note, this doesn't include the concept of a "bug"; that's a different topic.
* A cracked or shattered ruby gem is one concept that crossed my mind, but don't let that limit you.
* See the material at http://rubyidentity.org/ for the official Ruby logo. But PLEASE NOTE: While I will consider designs that use the official logo, I will give some preference to designs that do not, since using the logo means the whole work must be CC-licensed.
* It must include the title ("Exceptional Ruby") and the author's name ("Avdi Grimm").
* It must still be legible when scaled to thumbnail size - so not too busy.
* This book will be primarily viewed on screen. If it is printed it will most likely be printed on people's home printers.
* A plain white background is best - no full-page gradients or dark fills.