The NJ Archives Series contains one volume of marriages.http://search.ancestry.com/search/db.aspx?dbid=2794
The title of this database on Ancestry is Marriages 1683-1802. The actual book is titled 1665-1800.
This book does NOT contain all of the marriages for this period in NJ. Most of it is licenses, which were fairly early. There are also a particular section on Essex County. I would say that most of the marriages indexed here are from the 1740s to 1800.
If you browse the first 20 pages or so of this volume, you will find explanations of what is included and where other records may be found. The next 100 pages or more contain a detailed history of marriage laws and customs. This section is so detailed it even mentions Adam and Eve (and no, I'm not kidding).
You can search this database as you would any other. But beware that spellings can be creative and abbreviations are sometimes used for given names.
If you are looking for later marriages (i.e. after 1795), you probably need to search county records. After 1848, most marriage records were recorded with the state.
If you have a particular county/years you are searching, I may be able to help further.