Web/iOS: If you can't find the time to read the whole book, Blinkist takes you through the most important parts of non-fiction writing. The app is entirely human-powered, summarising lessons from the book in simple language, shortened for a quick read.
Blinkist actually has a pretty decent collection of books already on it, divided across categories such as popular science, business and career, politics and history, health and happiness, entrepreneurship, productivity and self-help and society. Arranged in a grid of tiles, you can see the author and book title along with a short excerpt. Click that and you get a longer explanation of what the book is all about and the option to read it.
Each book is broken down into a few chapters, manually written by field experts, Blinkist says. The summaries are actually pretty great; I checked out a few books I had read against Blinkist's take and they managed to get all the salient details in.
You can try out the app for free for 30 days, after which Blinkist costs $US4.99 per month or $US49.99 per year. Obviously, you should ideally read the whole book, but if you can't, then it's better than nothing.
Blinkist [Official site]