It varies widely. The O'Reilly eBook versions are very consistent. I really rely on the reviews on Amazon for the Kindle versions (there are often complaints o

It varies widely. The O'Reilly eBook versions are very consistent. I really rely on the reviews on Amazon for the Kindle versions (there are often complaints of layout issues in code examples and diagrams). O'Reilly is by far my favourite publisher/store for eBooks. If they can't lay out a certain technical book in a usable form in epub or mobi, then it probably can't be done. In those cases, I just use the PDF on my computer or on a large tablet (Nexus 10). It's all DRM free, multi-format so I can use whichever format is best for the content. For diagram/image-heavy books I usually default to PDF. In terms of non-linear reading, it's got to be printed books or PDFs with a proper TOC and bookmarks on my computer.