One issue that keeps me up at night—aside from school, plot holes, and oh-my-god-did-my-skirt-go-with-my-top-today—is whether being a Goodreads reviewer will affect my chances of being picked up by an agent. I NEVER bash an author in negative reviews, but I do have never-reading shelves for writers that I perceive to be rude to reviewers/bloggers (e.g. Kathleen Hale). What if an agent comes across a negative review of her client's book and decides not to rep me? Should I stop reviewing altogether?
well, no, but you're right to be thinking about this.
I've mentioned this before but it bears repeating: trash one of my client's books and we're done.
Now by "trash" I do NOT mean a well-thought out, well-written review that points out plot holes, or unbelievable characters, or lack of tension. Those are legitimate things to criticize about a book. I may not agree with your opinion, but I'm not going to add you to my fecal roster for writing them.
Where the line gets murky is exactly what you mentioned: never-reading shelves. Or "Authors I don't like" shelves. Or "Rude authors" shelves. Or "Authors who have spouses who should just shut the hell up" shelves.
Here you're not talking about the book. You're talking about your perceptions of an author's behaviour. You'll want to be VERY careful about that because as we all know from the Justine Sacco Twitter fiasco, things get taken out of context, or someone doesn't pick up on irony, things go viral, and soon bear no resemblance to reality. You don't want to be on the wrong side of that.
I think writing about books is an excellent way to hone your writing skills and get practice in how to talk about books. Stay on the right side of the professional line, avoid temptation to label any author with "will never read" and you'll be fine.
If you want to see what a good review that has some well-made points about one of my clients, here's our very own Colin Smith writing about Crashers by Dana Haynes. Colin is not a client, but he's a regular blog reader. Sadly, he was banished to The Great Pit of Carkoon last week, but I think he was rescued and returned. He was NOT banished for this review.