Lonely Planet guidebooks are nice to get a quick overview of a place, or find some things worth seeing and doing around where you are traveling. However, lobbing around an extra half a kilo or more isn't great.
I'm already carrying my e-reader, so wouldn't it be great if I could just save the relevant sections there?
However, while they do sell an official Kindle edition, I prefer using the paperback versions when planning my trip. So instead of buying it twice, I simple scanned the relevant pages at the office, then cropped them into a single paged ...