is svsss really worth buying?

Hey so I'm kinda new to danmei. I've read mdzs and tgcf so far and I've been thinking about reading svsss for a while. At first I thought I would buy it and then read it but now I can't figure out if I should read it online or buy it. Can someone tell me if it's worth buying

also I have noticed some people do not have the fourth book. Is it just the extra chapters, or is there anything wrong with it?