What law book should I read ?

Since there are several books called The Rule of Law I should clarify I'm pretty certain the above poster was talking about the Bingham one, which is a pretty soft introduction to the subject. Depending on your university it might still be more detailed than you need to know, and rule of law arguments rarely come up in private law matters.

I'd read some cases (there are plenty available at Bailii) since that's likely going to constitute the bulk of your course.

To add a bit of depth to your essays you could read A Very Short Introduction to Jurisprudence, which will likely be more than sufficient to add another level of argument to most first-year essays. I know an above poster said not to read jurisprudence but I guarantee he's not talking about that book, rather Hart, Dworkin, Kelsen etc (which I wouldn't recommend reading unless you've read philosophy before and enjoy it).

It's probably also worth doing a little bit of background research into the English legal system (i.e. the operation of statute and precedent, it's unlikely you'll need to know much detail) unless you've done A Level law.

Uh... other stuff which might be useful... a vague understanding of basic economics... the same for various moral philosophies (basically the sort of level to be able to recite shortly the difference between act and rule utilitarianism)... of course LtaLS is great for basic essay technique... you could read a wikipedia page on the differences between common and Civil law... the same for law and equity...

Finally, read Free Culture, it's ****ing GREAT.