In a previous post there was a short back-and-forth about guidebooks. Some people don't use them. I find them essential in preparing for a trip though -- even deciding where to go. I thought I'd point out Snarky Nomad's interesting post about how to cut up a guidebook into smaller, more portable chapters.
For those who prefer digital guides, I also wanted to mention that the Rough Guides offer a better ebook deal if you buy directly from their site, rather than Amazon. For the same price, you get three versions (MOBI, ePub and PDF), all DRM-free. I found the PDF version the most easy to read, because it looks exactly like the paper book.
On last year's trip to the Middle East, my numerous guidebooks were indispensable in figuring out which cities to hit, how to get around, which border crossing to use, and what to be careful of. On the other hand, I preferred tripadvisor for finding accommodations, and this year am using airbnb. Guidebooks maps CAN sometimes be useful, but so is Google Maps, and particularly Pocket Earth, which is great for offline navigation.