Aside from the Vital Record’s Index, Census records, and the International Genealogical Index (IGI), my favorite research aids include the following books (listed in no particular order):
1) The Victoria History of the Counties of England, edited by R. B. Pugh.
This multi-volume collection provides information on the cities, towns, villages and hamlets of the counties of England. Some volumes include historical village maps, photographs, architectural information about the local church and manor house, prominent people (including the vicars, local gentry, and other notables), and agricultural and manufacturing practices of the area. (I own just one volume of this set.)
2) Some Special Studies in Genealogy, edited by Chas. A. Bernau.
A friend gave me this tiny reference book published in 1908. It is full of little gems of knowledge about the different record types of value to the genealogist. The archives and payment fees are out of date, but the rest of the information in as current today as it was 100 years ago.
3) Child’s History of England, by Charles Dickens.
This charming history starts with the Romans and concludes with the year 1887. Here is a little sample:
“With the exception of occasional troubles with the Welsh and with the French, the rest of the King Henry’s reign was quiet enough. But, the King was far from happy, and probably was troubled in his conscience by knowing that he had usurped the crown, and had occasioned the death of his miserable cousin.” (Dickens, p. 175)
4) Nineteenth-Century Britain: A Very Short Introduction, by Christopher Harvie & H.C.G Matthews. Very short indeed, this volume is 177 pages including the index, but here you will find politics, religion, wars, economics, and people of the 19th century.
5) Ancestral Trails: The Complete Guide to British Genealogy and Family History, by Mark D. Herber. If you want to know about a topic, you will find it in this volume. He discusses record types, and archives. There are even illustrations in this great book.
6) Genealogical Research in England and Wales, volumes 1-3, by David E. Gardner and Frank Smith. I am lucky indeed to own all three volumes. The last volume includes paleography lessons, and a guide to Latin names and terms commonly found in Wills and church records.
7) The Phillimore Atlas & Index of Parish Registers, edited by Cecil R. Humphery-Smith.
This is my all time favorite research aid. This book has pre-1832 county maps which show the parish bounderies. It also includes an index of parish registers--the time period covered by the registers, their availability, the civil registration district of each parish, if marriages were indexed by Boyd's or Pallot's, and the time period of the registers included in the IGI. It is almost impossible to do British research without this book. This book was well worth every penny that I spent to aquire it!