So, there are lots and lots and lots of Mexican cookbooks out there. And I've been trying them. Here's what I think so far.
There is no question, at least to me, that you want Diana Kennedy's books if you're living in Mexico or if you want truly authentic Mexican food. You need a good source for fresh masa for a lot of her recipes, and she doesn't skip tricky ingredients, although there are some things she avoids or only calls for rarely (like jocoque). I have The Essential Cuisines of Mexico (which is coming out tomorrow as an ebook) and have cooked from My Mexico.
But I think Rick Bayless' Authentic Mexican is probably a better choice for some of American cooks than Diana Kennedy's. It's still good Mexican food, but it's a little simpler and tweaked just a little for North Americans.
I've also tried Pati's Mexican Table and it has some good recipes too, but I feel like it's a little more Americanized than Authentic Mexican.
I've also checked out various other books that go even further to appeal to North Americans and none have been amazing.
So if you want the real deal, get Diana Kennedy. If you want to cook good Mexican food but don't want to go too far, go with Authentic Mexican.
And I hope someday to get my hands on this one.