But don't fall into the trap of letting them dictate your travels – the first symptom of having capitulated to 'the book' is if you find yourself frequently saying, "But the book says..."
Not all information in 'the book' is correct and the authors who write them aren't always objective. Listings for accommodation and restaurants may be out of date (the prices usually are), suggested itineraries may not suit your interests, and many great places might be missed if you only travel by listings and suggestions in 'the book'. Be spontaneous and explore on your own, using 'the book' as it was meant to be used: a guidebook, not a manual. I found them incredibly handy for maps and information about getting from one place to another. When preparing for a trip, they're inspirational and can help you determine where, exactly, you want to go.
The same goes for advice from other travelers. On the road, I got plenty of it from other travelers: don't go here, this place was great, I hated this, I loved that... I learned that I loved what others hated, and vice versa. I realized that you have to find out for yourself. So if you take any advice, take this: take it all with a grain of salt.