Now I understand the impulse, we all want authentic, unique experiences, and how could we possibly get that from any mass-market paperback carried by so many people. But not getting a guidebook is still a mistake.
I've already talked about what's wrong with setting your main goal to be *trying no to be tourist*. This is closely related to that in terms of philosophy. Just because the tourists are doing it doesn't mean you shouldn't. Here's why:
Guidebooks will tell you more practical information, more conveniently, efficiently, and quickly than anything else you can find on the internet or pack in your backpack. True, there are other sources of information (local friends are the ideal) but a guidebook is better than nothing. At many points in your trip, if you don't pack a guidebook, nothing is exactly what you're going to have.
It's true, not all of the books' contents are gold. Restaurant and hostel/hotel information is often out of date, and will probably be decidedly on the beaten path by the time you read it. But those aren't the useful part of the guidebooks.
The useful part of the guidebook that you want immediately include the name and location of all transport hubs, local laws you wouldn't otherwise know about, local customs to know that help you be a respectful visitor, a brief (and usually hilariously written) history of the place you're going, a rough idea of how to ask for basic things in the local language, and here's the surprising one: the most common local scams travelers fall for, and how to avoid them.
It's that last one that all of your "cool" friends without guidebooks are going to wish they knew about. The rest, you *could* find with a lot of time, effort, and a stable internet connection. But a book is cheap, portable, easy to access, doesn't rely on electricity, and can tell you all of the information in a fraction of the time you'd spend otherwise. Time you can then spend actually enjoying your travels.
If the idea of getting a guidebook still sticks in you craw, just think of it this way: you have to know the rules before you break them.