I've been using this Simplify Gmail chrome plugin for a week now and I highly recommend it. I've been accidentally clicking compose ever since Gmail added the fly-in-on-hover navigation on the left. This plugin removes that and adds a floating compose button in the lower right. It removes several distractions around the edges and lets you focus on reading email—which is what you're there to do.
"After using all the UI richness available for such a long time to make beautiful and differentiated products, app designers have realized that the user's work, not their own, is the star of the show."