German law is the law of Germany. Germany's law system has considerably changed in the years after the first World War. Beforehand it was a monarchy with an emperor and a kind of parliament called "Bundesrat" (federal council). Do not confuse it with the nowadays "Bundesrat"! Then, in 1918/1919 Germany became a democratic republic. It got a quite liberal constitution ("Deutsche Verfassung von 1919" or -- mostly -- "Weimarer Reichsverfassung"). However, when Hitler became Chancellor he used the democratic system to erode it itself. The democratic republic changed to a dictatorship resulting in the second World War. 1945 WWII ended and the Allies intervened and took action in the legal system of Germany: They abolished laws from the Nazis which was not appropriate, mostly because it was racist. Then there was established the Parliamentary Council ("Parlamentarischer Rat"). It was constituted to form a new constitution. This happened in 1949 with the announcement of the "Grundgesetz für die Bundesrepublik Deutschland" (abbr.: GG; Basic Law for the Federal Republic of Germany). So, Germany is a democratic and federal social state (Art. 20 GG). It is also governed by the rule of law but that is not stated literally in the constitution. It is deduced from the way of law-making, the separation of powers, the basic rights and a lot more.
The law system in Germany is -- in contrast to the English legal system -- an inductive system. That means that law does not derive from decisions of judges but from the parliament. Although that is the main source of law today in the English legal system as well, there are differences. Judges in Germany are not allowed not to apply laws from the parliament -- even when they think it is not just. They can only ask the Federal Constitutional Court of Germany to declare it unconstitutional.
Explanatory notes 
In this book it can happen that there will be used the German system of referencing to laws. Therefore here is an overview:
|abbr./sign||German meaning||English translation||explanation|
|Art.||Artikel||article||used to point out the importance or when there is needed an additional hierarchy|
|§||Paragraph||section||It is not literally translated. But they are used equivalently.|
|Abs. ... or
roman upper numerals
|Absatz||paragraph||The same as above.|
|S. ... or
Arabic numerals (only when roman upper numerals were used for paragraphs)
|Var.||Variante||alternative||Mostly used when there are more than two alternatives because "alternative" just means that there are exactly two options if you translate it literally from the Latin origin.|