What I would consider a good guide book is one that is balanced and as up to date as possible. A book that doesn't lean to much to the negatives or positives, but is mostly neutral about the businesses, locations, and stuff it lists. Also, guide books have to be well rounded with the pictures to give the traveler an idea of the place they are going to be visit. For example, many guide books when they have a few pictures of the city of Santo Domingo, they only show Avenida Duarte and some Colonial Zone strip. That only gives people a sort of negative view in my opinion because the person would take a book like rough guide, read about how unappealing and unideal the city is according to the author, then see the pics of the "modern" town along Avenida Duarte and then the "old" town possibly Calle El Conde. The tourist would get the impression that any beauty in the City only exist in the colonial zone. Now, I know the Colonial Zone has that historic type of beauty, but I find the Malecon beautiful, and Avenida Winston Churchill, heck I even find Avenida 27 de Febrero beautiful and impressive and yet, no guide ever puts a picture of those places. I wonder how many tourist with some serious money are probably put off by the unbalance view the guides give. So yeah, a well balance book is a must. Even though I say a balance view is a must, the books should bend a little to the positive side. After all, aren't these books trying to attract more tourist to help these economies??
Now that you know what I like in a guide here are my favorites:
Moon Handbook Dominican Republic - awesome coverage in culture, cuisine, history, geology, literature, etc. Plus, the writer is very fair and balance with a slight positive pinta that makes the reader want to get up and hop on a plane bound for the Best Place on Earth, the DR.
Footprint Handbook Dominican Republic - again, excellent book that motivates people to visit the place.
I am not fully satistified with Rough Guide due to a heavy interest on Vodu (which makes the reader think that every dominican practice Vodu - we all know many dominicans practice "brujeria" but not Vodu), and the book has some inaccurate statistics like claiming a 90% poverty rate (which is false) and over exaggerating on the Crime aspect of things. I must say, their layout is excellent, if only some of the most important content in the book could be more accurate.