If there is one book I would recommend it is 'The Genealogist's Internet' by Peter Christian and published by the National Archives in Kew.
This is a comprehensive introduction and guide to researching British family history on the Internet.
The internet is proving an invaluable resource for anyone researching a family tree, but the sheer volume of information can make starting your search confusing and time-consuming. This much-expanded third edition contains everything you need to know about family history on the Web. It describes:
On-line records and web sites of national and local archives in the UK
On-line historical and geographical resources of interest to family historians
Services provided by genealogical organisations via the internet
How to use mailing lists and newsgroups to find advice and others who share your interests
How to locate genealogical information on-line
How to publish your own family history on the Web
This third edition contains a wealth of new material, including recent developments in on-line services in key areas such as censuses, wills, births, marriages and deaths records; historical maps; immigrant communities; and standards for on-line purchasing. It is the essential comprehensive guide to the internet’s resources for all family historians with roots in the UK.
On the books website you will find a list of its Contents, as well as a handy list of all the links contained within the book, as well as a bio of the author, Peter Christian, a Fellow of the Society of Genealogists.
I can guarantee you will find it an invaluable source of information for your researches.
Amazon.co.uk have it for £8.44 (normally £12.99) & Amazon.com have it for $18.96