I wrote a whole screen on how you should choose a book as carefully as you choose your toothpaste, but I suspect people want concrete advice. That follows in a later entry.
Here’s the general waffle:
Books to learn legal English /Bücher zur englischen Rechtssprache
This topic came up in the comments recently.
The question was, Which books can be recommended?, but the first question has to be What do I want to learn?
What do I want to learn?
Listen, speak, read write?
English law? U.S. law? Other?
Terminology?
A broad introduction or specific areas of law?
The court system?
How do I prefer to learn?
Reading? Reading a collection of texts or a continuous text? Find explanations of words in the book or in a dictionary? in English or German?
Doing exercises? Do I need a key to the solutions?
Why did the publisher publish this book?
Be suspicious about publishers adverts for books. They may say the book is for law students AND translators AND interpreters AND trainee translators and interpreters AND practising lawyers, but who is it really for?
They may say the book teaches British and American English, but does it really?
And dont be taken in by a catchy title – look at the contents (conversely, a Denglish title may be the work of the publisher, not the author)
Can I find a course?
If you can find a legal English course at your university or elsewhere, that is probably the way to learn about legal English with the least friction. You will probably have a textbook and an incentive to read in advance and review afterwards, and to talk in English about what you read.
What type of book is available?
Books in German on English or US law, giving the English terminology, sometimes with a language index
Books in English on English or US law, sometimes intended for readers from other legal systems
Course books for law students in non-English-speaking countries: some have a German bias and some German translations, some are for a wider audience. Contents often contain comprehension texts and language exercises.
Reference works in English
Books on legal terminology
Dont forget you can find all kinds of materials on the Internet, including legal weblogs, podcasts, videoclips at Court TV (and presumably on Youtube too).