I'm always reading about 5 books in parallel, depending of my mood, the context and my focus.

Usually:

  - biography or fiction book that I listen to while driving

  - hard science book when I know I can focus for a few hours. (I.e. Quantum mechanics or advanced algorithms)

  - 1-2 business or technical book that I read on kindle (Either from PC, ipad or my iphone)

  - various blog or pdfs open on my pc / iphone

The business / technical books are the ones that I read the fastest because I can skip useless chapters and they're always one-click away when I have a few minutes to wait.

The hard science are the ones that take the most time.. sometimes it can take me weeks to read a few pages, and I often need to do side research to understand what I'm reading.

I think the fact that I have different choices help me read more because if I'm not in the mood for one thing there's usually something else interesting. If I don't have interesting books then I'm more likely to waste time on reddit / HN / twitter. (I still browse HN from time to time when things are compiling though :D)