@aspiderjonny I read the entire story, and I try to grab most of the images from the first couple of chapters. There are a few exceptions to this though, especially if you can see the artist's growth throughout the comic. I usually go through the whole comic more than once, looking for the best images for the review, and try to leave out important scenes that would give away any spoilers (sometimes this is difficult, it all depends on the layout of the comic itself).
This is also why it takes me two weeks to release one review, well, that and school life.