This is another place where authors can post reviews of their books and give away advance copies for review. They don't need to be advance copies, and anyone can post but they do have preferences for professional books from publishers over self-published authors.
This one doesn't come with a signup bonus, which means that you are giving away copies of your book purely for reviews, but it also means that it functions more like a NetGalley type of website than having a cross-over benefit like on Goodreads or Amazon. This is purely for giving away copies for review, not as a way to give things to your followers or run a contest to give out an award. That being said, it isn't a bad option by any means and can actually be better in some ways because readers know exactly what is expected of them.
The reviews are usually pretty good because readers have selected to read your book specifically. However, the only obligation is to add a review on the LibraryThing website, which means it is hit or miss whether or not the review will end up on any other platforms. And, the LibraryThing platform isn't somewhere that people are going to go to find book recommendations very often, so in general this could be a lot of copies given away for very little return.
This is another category where LibraryThing falls short, because there is no real outreach built into the system to encourage sharing and viral marketing. It has an enclosed audience that usually requests books and doesn't seem to be growing very much, at least in the indie author sector.
Giving Away Copies
This is actually something I would like to caution people about, because there are some untoward people who use LibraryThing to try and trick authors into giving them money. Essentially, what they do is request copies of books. Some authors rather than sending a .mobi or pdf file of their book will actually gift a copy to the reader. This is something that Amazon offers to make it easy to give away review copies, but there is a caveat to it because the person accepting the 'gifted book' could actually just exchange it for an equivalent gift card. So, they just request for every book offered, and whenever an author sends them a gift they just exchange it for money.
If you use this website, use something like bookfunnel or instafreebie to deliver the books, and make sure it is a watermarked copy so they can't give it away or sell it to another unsavory individual. Technically, these readers are doing nothing wrong, but I don't think we will find many people who want to defend this practice because it means they are completely neglecting the actual exchange they agreed to and making it impossible.
Is it worth it?
Tough to say for this one because some of the negatives are fairly substantial. In general, I've given away hundreds of books through this service and only received a handful of reviews in response, so when I'm working on my future efforts I'll probably drop this service and focus more on the other things I use that actually work.
That being said, it isn't terrible, and it can be a great way for a new author to get his feet wet and start the process of building readership. That being said, never give away gifted copies of your book. Send mobi files through a protected service or smashwords or something similar.