I have the Mexican food made simple and I love it but I don't think it's all the authentic tbh, (XDP is South American) but easy to make of you have access to the ingredients and really easy to follow.
I've had Mexican Food Made Simple. It's rubbish tbh. I wasn't inspired, and the few things I've cooked from it doesn't taste good. I remember a chicken salad from the book. I have cooked a similar dish from Nigella. But Nigella's version is much simpler and tastes better. I have sold my book second hand back on Amazon.
If you want a good Mexican cookbook, look at classics like the ones from Diane Kennedy.
I love Mexican Food Made Simple! Such delicious flavours. I do think though that you need to buy chipotle chiles and make chipotles in adobo ahead of tackling a lot of the recipes (she gives a recipe for that too, it is easy and really tasty), as a lot of recipes call for a couple of spoonfuls. This might mean a trip to a specialist shop (in London you can get them from Borough Market or Casa Mexico in Bethnal Green, or I use mexgrocer on the Internet).
I think her second Mexican book is good but the recipes seem to be geared to large groups eg serves eight. Which may or nay not be helpful.
I also agree to an extent with an earlier poster that Diana Kennedy is the bible for Mexican food!