Best Open Source Web Software for a small book club?

I am a web entrepreneur/freelancer who does websites for clients from time to time. I have been asked to create a website for a local book club.

I want to know if anyone has a particular software package in mind that would be relatively lightweight and easy to use for the members (who are not extremely tech savvy)

Features:
*Reading List
*Some sort of forum capability
*User accounts

I am very familiar with wordpress, but I wanted to see if there was an even lighter solution out there. I have also considered Google Sites…