For North America, there are a multitude of field guides to choose from for birding. Field guides can be broken down into two main categories and two sub-categories. The two main categories are ones that cover all of North America and ones that cover a particular sub-region, say a state or specific park. These field guides can then be broken down into ones that use drawings to depict the birds and those that use photographs.
There really is no “right” or “wrong” field guide to use. Each one offers pluses and minuses. With drawings, often specific field marks can be illustrated in a way that emphasizes distinct features. Field guides with pictures in them are truer to real life and can be shown in different angles and lighting more similar to what you’d expect in the field.
Of course, there are other features that make a field guide worthwhile. How recently they’ve been updated plays a key role as birds are often split, lumped, or just have their name altered. Plus, if a field guide shows range maps (which are always good when they do), these too can change over time.
But, the most important feature of a field guide is that it works well for you. We’ve found that in order to really study birds well, multiple field guides work best. (And it’s always handy to have one in the car, one in your kitchen, one in your living room…)