More than a quibble?
I’ve been working through David McFarland’s book on JavaScript and jQuery the last week or so and while the book itself is great (e.g., clear explanations, good tutorials), I’ve got a usability quibble with it.
I bought the digital version from Amazon. However, with no Kindle Reader, that meant the experience would be delivered through Amazon’s Kindle-for-Mac tool. But when I got to the sample code snippets, the font size was so small that it rendered it practically invisible.

From a learning standpoint, the code samples seem just about as important as the explanations that surround them. I guess in this sense, maybe it’s more than just a (usability) quibble.
Perhaps this is just a Kindle-for-Mac issue, but it would be nice to at least have a toolbar option for modifying point-size.