George RR Martin has a thousand times my clout (literally 1000x, no hyperbole here) and his glowing recommendation on the front of a book in no way guarantees it will fly. The Dinosaur Lords bears the legend, "It's like a cross between Game of Thrones and Jurassic Park!" from GRRM himself, and has not had runaway success. My own One Word Kill basks in the glow of "I enjoyed the heck out of it. Mark is an excellent writer!" from GRRM (in the Amazon listing - it came too late for the cover), and yet is not a New York Times bestseller.
The stars have to align. I gave a push to Senlin Ascends that I believe did help it on its way to much greater acclaim. But my love for Master Assassins was not able to repeat the feat, despite my many exhortations on the book's behalf.
There is, however, an enduring and massive overestimation of the impact of my approval among many hopeful new authors. Let me put forward this example in all its statistical glory in an attempt to bring us back to reality.
I'm a fairly popular author. People pay MONEY to read my books. Enough so that I can live off the proceeds. You would think this would mean that, when I offer my writing for free, people would jump on it. At least some of them. I've sold nearly two million books and must have hundreds of thousands of readers. So how many do you think would try on my recommendation not somebody they've never heard of but me: Marky?
On Wattpad I've been putting out chapters of a book I started writing called Jacob's Ladder. I think it's good. I've been alerting the 9,830 people who follow/friend me on Facebook to each chapter as it's posted. I've also been posting about them to the 7,506 members of the Grimdark Fiction Readers & Writers group on Facebook where I'm reasonably popular.
I also have 2,815 followers on Wattpad itself who get alerts when I post the chapters. And I've tweeted about each chapter to my 28,600 followers on Twitter. And I've blogged on Goodreads about it where I have 48,029 followers.
I posted chapter 5 two days ago and it's had 21 views (which are not necessarily reads) at least one of which was me.
All of which I throw out there to demonstrate how ridiculously hard it is to be heard and to have that audience act.
Now, new authors, consider how much of an impact the weeks this slow reader spends reading your book will have on your sales when condensed into a line on the cover...
None of this is to say that I won't read as many fantasy books as I'm able, and that I won't blurb the ones I like. I will, can, and do. It's just to say that it's really not likely to make more than a whisker of difference so that "my life is in your hands" vibe that sometimes echoes through read requests is really misplaced. Your book needs to be crack. It needs to be eye-heroin. But that's just the entry price - beyond that it needs the stars to align, it needs luck, it needs lighting to strike seven times in the same damn spot. It needs, the magic that nobody understands and might just be random chaos, the magic that decides which good books fly and which sink. I am not that magic.