Richard Brittain, a former champion on the TV programme Countdown, travelled from England and used Facebook to find Paige Rolland, 18, at her work.
He admitted assaulting Miss Rolland with a bottle to her severe injury on 3 October 2014 at Asda, Glenrothes.
Sheriff Martin Jones deferred sentence until a later date.
A motion for bail was refused.
Glasgow Sheriff Court heard Brittain uploaded part of a published book of his called The World Rose onto a website called Wattpad, where people can read and critique literature written by others.
Miss Rolland read the excerpt of Brittain's book and left comments about it.
Procurator fiscal depute Harry Findlay said: "The complainer had read some of that material and gave feedback of what she thought to be the merits or otherwise of the book.
"The feedback was negative. What followed were comments made by the accused which give an indication that he was displeased."
In October last year, Brittain went to the Asda store Miss Rolland worked in after she began her shift.
Mr Findlay said: "He went to the alcohol aisle and picked up a bottle of wine, he then went to the aisle where the complainer was working.
"He approached her from behind, she was kneeling down collecting cereal from the bottom shelf of the aisle.
"While doing so, the accused approached without warning, any provocation or words and he struck the complainer on the back of the head with the bottle.
"One blow. It made contact and the wound bled immediately and she had a moment of unconsciousness."
Miss Rolland was taken to hospital suffering from a cut to her head and treated for a head injury.
The court also heard that a month before the attack on Miss Roland, Brittain stalked a university classmate, Ella Durant, 23, who moved from London to Glasgow.
He used her Twitter and Instagram accounts to find where she worked and turned up on two occasions to speak to her.
Brittain, whose address was given as Palgrave, Bedford, pled guilty to engaging in a course of conduct which caused Miss Durant fear or alarm by repeatedly pursuing her, approaching her, following her and publishing a story about stalking her in September 2014.
Defence counsel Michael Meehan told the court that in relation to the message from Brittain to Miss Rolland after she criticised his work, his client pointed out she had not read the published version and asked her to remove her comments.
The court was told he also contacted her in September this year with an apologetic message.
An author tracked down a teenager in Fife and hit her over the head with a bottle after she gave his book a bad review, a court has heard.