I have read all of them. The first was pretty good and is impossible to put down. The second is intense and fairly good. The third is alright.
The last one is horrible! She goes against everything she says cannot happen. I was hugely dissapointed. It was a struggle to read. The characters changed and it was all around poor writing.

I will not give away any of it. But I really hated the last one.
Its not risque. She keeps it on the down low and lets you imagine what happened.

While this is not my favorite series its okay. I have no desire to read it again after the last one. Keep in mind I am 27 and love Youth fiction. The gals at the library where I worked this summer all share the same opinion of the last one. We were all annoyed with Stephenie Meyers after reading it!

RIP Peeps