I'm going into my second year and I cannot stress the importance of working through the reading list over summer if you have it available and have the time to do so. Of course, if your aim is only to pass first year, then don't bother, but if you want to get good grades then getting as much reading done in summer will leave you with more time during the term to do the extra readings and study the topics in more in depth. That's what gets you good grades.
Also, doing the reading before the relevant lectures is great anyway because you are familiar with the topic but you also know which bits are heavily covered in the text and which bits aren't so much, so you can take really effective notes based on the content you already know you have.