Here is a new link to the book. I could tell it was changed and also new books that have been published by Grupo León Jiménes have been added to the link.
Grupo León Jimenes
In brief this book is completely in Spanish and it's a well-researched compendium of the sociolinguistic aspects of Spanish spoken in the Dominican Republic. As you will note in the thread I did a thorough review of the chapters that I believed would give people insight however, I did read the book in its entirety as a means to compare sociolinguistic aspects of Spanish spoken elsewhere in the Americas. Depending on your language background this book is an ideal gem for linguists, grammarians, educators and philologists. If you have a strong background in languages and specifically Spanish it will be a priceless gem for you to read.
The book touches on grammar specifics as they relate to Dominican Spanish. A classic example is sentence structure that is typical of Dominican speech patterns and in many cases Caribbean Spanish (specifically
las islas antillanas), the excessive usage of certain pronouns in this case 'tú' that's because the [s] is dropped, however, that is a property of informal speech. The [s] is dropped by most speakers but must always be written. If it's not when required it's incorrect. An example is 'tú dice' that's what you will hear but it s/b written 'tú dices'. There are other phonetic features such as the changing of [r] to [l] in words but that’s only in a certain region of the country.
In brief specific to your point about understanding some Dominicans and not others as well as Spanish speakers in Michigan, this concept falls under the umbrella term of language varieties. Many factors influence the way people speak i.e. education, socioeconomic differences, region, the history of the way Spanish evolved in one area of the Americas as compared to another area just to name a few factors. Dominicans do speak fast as compared to xxx but that speed could be accommodated the more you adjust to the language and the different ways it's spoken. The speed of language could also be very subjective and what's considered fast to one person may be a comfortable pace to another observer. IMO there are much faster Spanish speakers than Dominicans in very general terms.
-LDG.