Travel Guidebooks are an invaluable resource for tourists and travelers.  They can help you find accommodations, transportation, great restaurant options, and all the top attractions.
The good guidebooks, like the ones below, will also give you insights into what the locals prefer.  These are the top guidebooks from our own experience and from our readers' preferences on our Travel pages.  
Lonely Planet guidebooks are our go-to source for top-notch travel guides.  No matter where you're traveling in the world, you'll be able to find a Lonely Planet book to guide you.  
Since 1973, Lonely Planet has become the world's leading travel media company with guidebooks to every destination, an award-winning website, mobile and digital travel products, and a dedicated traveller community. Lonely Planet covers must-see spots but also enables curious travellers to get off beaten paths to understand more of the culture of the places in which they find themselves.
Whenever we travel to Europe, we always bring along a Rick Steves guide for each destination.  He also has some great free audio tours you can download from his site.
Rick Steves advocates smart, affordable, perspective-broadening travel. As host and writer of the popular public television series Rick Steves' Europe, and best-selling author of 40 European travel books, he encourages Americans to travel as "temporary locals." He helps American travelers connect much more intimately and authentically with Europe -- and Europeans -- for a fraction of what mainstream tourists pay.