"Passion starved Twilight Girls crossing over to a world of high withers, rippling hindquarters and glossy coats." · 8:31am Mar 7th, 2019
The most surprising fact is that quote above is not from an EqG / HiE Fanfiction.
That's a real quote from a real book.
That you can buy.
On Amazon.
The Big Book of Lesbian Horse Stories.
The reviews though suggest that this is somewhat misleading though.
2.0 out of 5 stars
Not as arousing as it sounds
April 20, 2013
Format: Paperback
Not as arousing as the title would have you believe. Plus, it is no larger than a regular sized book of lesbian horse stories.
3.0 out of 5 stars
Don't believe the headline!!!
May 27, 2014
Format: Paperback
Despite what this book's title would have you believe, it is not a big book about lesbian horses and the people who mount them (not THAT kind of mount, mind you); it's rather a moderately small book of heterosexual horses and the homosexual women who spend a lot of time riding horses and no time riding each other.
Damn clickbait Amazon!
If only there was a website with stories about lesbian horses.
Small, pony sized ones.
Little ones even. 
I knew about this book. Disappointed to see it doesn't live up to the hype.
Wtf
I wish I still had enough innocence to be surprised.
Mind you, Amazon is full of patently unreal books…
So, no Human on Mare lesbian action?
Pass.