Within the category of secondary legal resources are practitioner's text and academic texts. The link below will help you to understand and identify practitioners' texts.
Secondary sources are a great place to start for getting background information on a legal topic.
For each legal topic you will find there will be a large number of textbooks available. It is likely if you are studying that you will work from a reading list and there will be textbooks recommended for you on there. However there are a number of practitioner's textbooks for the major legal topics which are seen as an authority on a subject. The following are examples of texts on legal research.
There are many encyclopedias within the law. These looks to sort the law into organised topics and to provide a thorough explanation with links through to other sources. The main one for England and Wales is called Halsbury's Laws of England and this is a large multi- volume work which is arranged by broad subject. The structure of it is very good in building an understanding of the law, all topics start out with an introduction and then the first subsection is the law 'in general' before moving on to more specific areas. There is a basic definition the law with links through to cases and legislation.
These are summaries of cases, legislation and commentary arranged either by topic or by date/topic. These can be useful if you wish to get an overview of legal material for a specific subject.
Treaties can cover many different legal subject areas and can be multi-national or bi-lateral (between just 2 countries). It is always worth starting with the organisation that created the document or a source for one of the countries.
You are likely to have to read a number of articles if you are researching the law. These have the benefit of being able to focus on more specific topics of law, being able to be published more quickly that books in the event of an important piece of legislation being passed or a case being decided.