Yes, of course it is. It's in the name for Pete's sake. BUT is it good for aspiring writers? I'm still going to vote yes, even though I think there are some potential pitfalls.
Where it is absolutely good: Groups
I'm in a couple of YA groups and not only does this connect me with folks who would be my potential readers, it connects me with books in my chosen genre. With a new book assigned every month, I keep up on my reading and while I'm reading, I think about the book in terms of writing, story and characterization because I'm going to have to discuss it all later. They don't take a vague "I liked it," or "I hated it," as an answer. You better have reasoning as to why you felt that way or consider yourself shunned from the group.
Identifying aspects of what I do or don't find appealing about a book helps me improve my writing. I might notice how an author has a lot of shoulder shrugging and nodding going on in their novel, and then look back at my own MS and see the same nervous ticks.
What other people have to say about the book is helpful too. These are my readers, and they read a lot of books. The leaders of my groups have about 700+ books a piece under their belt, and they'll be the first people to point out tired story lines, cliche characters, and all around bad writing. They'll also share what they would've liked to see, and I take some of these ideas and try to incorporate them into my own writing. Give the people what they want!
Where it can be iffy: Reading other reviews
I am certain I'm piling up some bad karma points because some of the one-star, asshole-ripping reviews are hilarious. Even the shelf designations people give to books are somewhat funny, ie, the shameful-shelf-get-rid-of-it. And after I read one of these reviews, wipe the tears of whimsy from my eyes, I gasp and think, "When I get published, someone's going to write one of these about my book." Ouch.
Of course, below that one-star review is a five-star review contradicting everything the previous reader said. This reminds me that the publishing industry is SO subjective. I need to keep plugging onward and not get beat down my the rejections.
HOWEVER, when I read a book, give it a low rating and see it has an overall rating of 4+ stars, I think, "I can do better than this. Why are they published and I'm not?" Commence pity party. And a pity party is always a bad place to be in.
One thing I do love about reviews is when I make a note of poor characterization or lack of description and read five other reviews in agreement, I know my editing eye is in pretty good form. I can apply that to my own writing.
Where it could be bad: Writing your own reviews
The first rule about being on submission is don't blog about being on submission. The second rule about submission is DON'T BLOG ABOUT BEING ON SUBMISSION.
I don't. Because editors could type my name into Google, find my blog and see that my novel has been rejected by twelve others. But then I go onto Goodreads, write a less than glowing review of a novel that happens to be on the list of one of the editors considering my book. That has to be just as bad, doesn't it?
I see a lot of five star reviews on Goodreads for everything and wonder if the reader really likes all of those books or if he's just trying to gain some brownnose points for ARC giveaways or publishing presence. I might be lighting my MS on fire, but I can't do it, and personally, as a writer I would want to know what someone hated about my book so I could fix it in the next one.
I try to make my reviews honest and personal and always point out positive and negative aspects of the book. But it's true, there have been some I wanted to refer to as a "stinking waste of trees," and held back my typing fingers. For those books I follow the rule of, "If you can't say anything nice, don't say anything at all."
What about you? Are you on Goodreads? Friend me if you want to share reviews!