You've got a choice of Sibley ( either the 'big' one that covers the whole of Nth. America or the Eastern or Western, pocket sized ones ), National Geographic and some photo guide ( hmmm, I'll say no more

). North American birders seem fairly evenly split between Shirley and Nat. Geo. I prefer Sibley, even allowing for the 'strange' colour reproduction on some species, but, like many things, it's best to get a look at as many as you can to find the one you're comfortable with.